So I'm gonna try and keep this as brief as possible because no one got time to read a massive essay.

I love manga but recently I have become, shall we say, disillusioned with it. I only keep up with a few series I really enjoy and have regular(ish) updates like Assasination Classroom and Blue Exorcist and have been finding it really difficult to pick up new manga due to lack of release (such as Iris zero, so good, but nothing new has come out!) or I have just become much pickier in what I read

So please, recommend me something good to read, across any genre except hentai, yaoi, yuri, horror, shonen ai or shojo ai

My requests are is that there is a good plot with plot and character development and that it contains female leads that aren't completely useless (looking at you bleach) and who aren't objectified (you know, have a massive rack and constant up the skirt shots)

One of my fave series that fulfills this criteria is Full Metal Alchemist, nothing has yet beaten that as my all time favourite manga

Cheers 🙂

Past series that I have hated include but is not limited to:
Animal Jungle
Black Bird
Code: Breaker
Himitsu no Ai-chan
Nousatsu Rock Shounen
Vampire Juujikai
Akagami no Shirayukihime
Basara
Diamond Dust
Hana yori Dango
Hana-kun to Koisuru Watashi

I'm going to suggest some of my favourites

Angel Densetsu (Seriously hilarious, please don't let the art put you off!)
7 seeds (By the same author as Basara, but basara can't hold a candle to 7 seeds imho)
Kimi ga Uso o Tsuita (a personal favourite)
Principal (A shoujo I really like)
Okoborehime to Entaku no Kishi (Strong female lead. You'll like this you liked Joou no Hana)
Banana Fish (Gritty and realistic. Again, the art isn't the best but it's got an AMAZING story)
Eden - It's an endless world! (Another gripping manga)
If you're in the mood for some Shoujo, you should check out works by GEORGE Asakura (I really like Teke teke rendezvous) or Sakisaka Io.

One of my all time favourites is Hoshi no Samidare, a.k.a. Lucifer and the Biscuit Hammer.

It is a completed seinen series that I think matches most if not all of your criteria and, based on what you've listed as manga that you enjoy, I think that you might like it.

The only problem would be that, as it has finished and not been cancelled (so everything is properly resolved), once you finish reading it there won't be any more - though that hasn't stopped me from reading it about 5 times.

Yep, FMA sets way too high standards XD
Here are some manga that I liked:

Ongoing:
Pandora Hearts A shounen with a bit of shoujo art about a fantasy world and a boy who has formed a deadly contract with a rabbit-girl monster: this synopsis sounds stupid and generic, but it's because this manga is actually pretty difficult to describe. Gorgeous art and a balanced cast of males and females, everyone has their own strong and weak points; the story is interesting and you can expect a lot of plot twists. I'm a bit behind the current chapter myself, but what I've read so far has been really good. The character grow a lot during the series.

One week friends It's a delicate story about a girl who constantly loses her memories and a boy who tries to befriend her. If you like the slice of life genre, this one should be of your taste.Even with this premise there's still a lot of character development.

What about Yandere Kanojo? A funny comedy about a plain guy and a yankee girl dating. The art is not great but that's a plus because there's no risk for the girls in the story to be objectified, and the comedy can stay the funny type. There's space for character development too.

Butter!!!: a simple story about a bunch of highschool students who end up in a ballroom dance club for various reasons. No big drama and character driven. The only problem is that releases are a bit slow for this one.

Completed:

Too bad Double Arts was axed, because it had the potential to become one of the most interesting ones in the fantasy genre. I hate rushed endings but I still liked this manga very much, and it says a lot about its quality. Interesting premise, good art, quirky characters. It makes you wonder what happened to the mangaka to end up with Nisekoi 😔

I second Angel Densetsu and Hoshi no Samidare (even if there is a bit of "panty comedy" in the latter, but nothing out of proportions), and add Kekkaishi, an often overlooked shounen with interesting plot and character.
Hope you'll gain your faith again XD

My current top 3:
Fullmetal Alchemist
Pandora Hearts
3-gatsu no Lion

Since you like Assassination Classroom, check out the author's earlier work, Majin Tantei Nougami Neuro. It starts with bad art, but it quickly improves. More importantly, it's far more weird / unusual (in a good way) than Assassination Classroom.

Some I didn't find in your lists after a quick peak. It's a varied bunch:
Hunter x Hunter (you can go with the anime here)
Toriko (very original)
Fairy Tail (very shonen, lots of unavoidable fanservice)
Zettai Karen Children (espers)
AKB49 (boy infiltrated in idols group)
Pretty Face and Mx0 (same author who has a knack for guy undercover)
Magi (fantasy with arabic tones)
World Trigger (you like Blue exorcist...)
Skip Beat (a classic of showbiz)

I'm surprised you haven't read Chang Ge Xing then, and here are a few more:

Mahou Tsukai no Yome (Ongoing with regular releases, but manga is released monthly so not a lot of updates)
Sidooh (Ongoing with regular releases, but only one female lead who is really cool)
Chrno Crusade (Complete)
Hellsing (Complete, two female leads, one who is always bamf and the other kinda objectified in the beginning but really comes into her own later)
Suiiki (Complete)
Majo (Complete)
Immortal Rain (Complete)
NG Life (Complete, same author as Akatsuki no Yona and it's the one reason Yona is not on my "Unfinished" list)

And if you're not that into manga anymore you should try out web comics, and I don't mean webtoons. There're two in my sig, Unsounded updates three times a week and Ava's Demon updates once a week. The art in the two is quite beautiful and refreshing after reading so manga with similar art.

Must Read Webcomic:
Unsounded

Lists:
Reading
Complete
Western Webcomics

Here is my up to date mangaka master list (now in my signature):
Have faith!!! and never forget that Euro/US Comics are great too.

Josei: Hachimitsu to Clover Finished
Seinen: Berserk
Shojo: Mars Finished
Shonen: Rurouni Kenshin Finished

Action: Hellsing Finished + Shi ga Futari o Wakatsu Made
Adult: Oyasumi Punpun Finished + Natsu no Zenjitsu
Adventure: 7 Seeds + Hunter x Hunter
Anime: Cowboy Bebop Finished + Ginga Eiyuu Densetsu Finished
Anthology: Hi no Tori Incomplete (still 10/10) + Otoyomegatari
Bande dessinée: Largo Winch + Blacksad
Biography: Kakukaku Shikajika + Steve Jobs
Chambara: Azumi + Mugen no Juunin Finished
Civil disorder/Revolution: Innocent (SAKAMOTO Shinichi) + RideBack
Comedy: Dr. Slump Finished + Ore Monogatari!!
Comic(US): The Walking Dead + Animal Man Finished + Best international author
Comic Industry: Bakuman Finished + Even a Monkey Can Draw Manga Finished
Cooking: Bread & Butter
Dancing: Ballroom e Youkoso + Subaru
Drama: Boku no Chikyuu o Mamotte Finished + Paradise Kiss Finished
Ecchi: Jigokuren Finished + The Penisman by ISHIDA Sui
Educational: Crimsons - Akai Koukaishatachi Finished + Hadashi no Gen Finished
Fantasy: Ookami to Koushinryou + Spirit Circle
Gender Bender: Kanojo ni Naru Hi Fantasy + Nicoichi Real life
Harem: Ooku + Sayonara Zetsubou-Sensei Finished
Hentai: Wain no Kachikan Finished + Shoya
Historical: Kento Ankokuden Cestvs + Ookami no Kuchi: Wolfsmund Needs more views!
Horror: Dorohedoro + Kiseijuu Finished + Best ending.
Light Novel: Baccano! (Novel)
Magic: Ran to Haiiro no Sekai Finished
Manhua: Wolf & Mary Finished
Manhwa: Princess + Shin Angyo Onshi Finished
Martial Arts: All Rounder Meguru + Gunnm Finished and turns into one later
Mature:Yamikin Ushijima-kun
Mecha: Shin Seiki Evangelion Finished + Kidou Senshi Z Gundam Define
Medical: Iryuu - Team Medical Dragon + Jin
Military/Police: Kidou Keisatsu Patlabor + Yokokuhan
Mono no Aware: Yokohama Kaidashi Kikou Finished + Yotsubato!
Movie: Akira + Mononoke Hime
Music: Nodame Cantabile Finished + Sakamichi no Apollon Finished
Mystery: Kiss & Never Cry + Shingeki no Kyojin - Before the Fall The best version
One-Shot: Watashitachi no Shiawase na Jikan Finished
Psychological: Billy Bat + Best japanese author + Liar Game Finished
Romance: Last Game + Sunadokei Finished
Sci-fi: Uchuu Kyoudai Hard Sci-fi + Ghost in the Shell ARISE Needs more views!
School Life: Angel Densetsu Finished + Kareshi Kanojo no Jijou Finished
Shounen Ai: Tokyo Babylon + Finished Zankoku na Kami ga Shihaisuru Finished
Shoujo Ai: Honey & Honey Finished
Slice of life: Sensei no Kaban Finished
Smut: Sora wa Akai Kawa no Hotori Finished
Social Commentary: Saikyou Densetsu Kurosawa + Part 2
Space Opera: Five Star Monogatari + Seikai no Monshou (YONEMURA Kouichirou)
Sports: Ashita no Joe Finished + Real
Supernatural: Mushishi Finished + Hagane no Renkinjutsushi Finished
Survival: Gantz Finished + Jisatsutou
Tragedy: Gunslinger Girl Finished + Kisshou Tennyo Finished
Train-wreck: Wolf Guy - Ookami no Monshou Finished
Webtoon: Blind Faith Descent + Superior Day - Finished

Every author is on it once so if you like what you read go for the rest. (Hey ElanorR)

I also read EU/US comics and am a librarian.
Manga-Masters, My ANN-Lists + Imdb

karakuri circus, tokyo ghoul

Quote from 3kul

One of my all time favourites is Hoshi no Samidare, a.k.a. Lucifer and the Biscuit Hammer.

This. Also Battle Angel Alita. Perhaps Emma.

One of my all time favorites

Natsume's Book of Friends

i would go one piece they lead women do have big racks later but they don't do anything in the manga that they would in an anime. Also character development is top notch

Quote from mikako17

And if you're not that into manga anymore you should try out web comics

It's not that I'm not into manga anymore, don't get me wrong, I still LOVE manga, but I consider myself a feminist and a lot of mangas I read just destroy my faith in humanity. Like in bleach, all the female characters who are supposedly strong also nearly always need to be saved by a male character and the objectification of women is crazy in manga. Completely unnecessary up the skirt shots, zoom ins on cleavage, tiny waists+massive rack+the skiimpiest outfit ever, even if the character is supposed to be a warrior, her armor is so useless and would provide no support whatsoever for her supersized breasts.

Also, I've found a lack of character development in depth in many female characters, reasons why I dropped series such as kimi ni todoke, girls of the wilds and nisekoi

Likewise, I like Iris zero

Most of these are more slice of life:
Ame nochi hare
Ashita no Ousama
Bokura no kiseki
Glass Mask (venerable)
Katsu
Patlabor

ai yori aoshi
aqua/aria (not that much of a plot, but a nice manga)
Faster than a Kiss
Katsu (adachi fan here)
Host Club
kimi wa pet
Koukou Debut
Mirai Nikki
Mx0
Shaman King (the main heroine have appears very little, but is strong)
Superior
Usagi Drop (child care manga)
W-Juliet
Claymore
Arakawa under the bridge
3 Gatsu no Lion
D-Frag
Meitantei Conan
Shinryaku! Ika Musume (comedy manga)
Skip Beat
Yotsubato! (slice of life manga, almost no plot what-so-ever)

Also you may want to see these animes, both with nice female leads:
Seirei no Moribito
Juuni Kokuki