The only major drop in 'quality' that I perceive is that we get way more novel adaptations, which aren't really paced right to be a serialized comic. (And often cut details that make the plot more coherent)

That being said my preferred era is late 80s/early 90s but I think that's just nostalgia

I honestly think it has only gotten better over the years. I read a lot of romance manga and in recent years we've gotten a lot of them where the main characters actually communicate and are more forward with their feelings compared to early 90s/2000s where they would take 20 volumes to confess their feelings and talk.

Graphics sometimes are much better, but for the stories... There weren't well-thought and profound plots since Death Note. And comedies since Ranma 1/2, Dragon Half.
Also, not many experiments nowadays. Publishers demand stable-income stories, like generic isekai's.

Drawing quality improved. Paper and cover art improved. Story, hm, not so much. There are great mangas nowadays but some lack in characters development and story in my opinion.

No difference at all. There is a bunch of total trash and follow-the-trend shovelware but that was always the case. The shitty trends of today will give away to the shitty trends of tomorrow and ESP and mechs being shoved into goddamn anything in the 80s and 90s wasn´t better than isekai being inserted into 85% of all fantasy manga rn.

Some of the best manga of all time are also being published rn. Darwin Jihen only began in 2020 and is being showered in awards for a reason.

everything is better (for other people)
for me, I have to find the needle in the haystack
but the teenage me would be super impressed and would never see the light of day with vitamin deficiencies etc etc

I voted "In general, no, but some new manga are really bad" because some of the stuff produced in the recent uptick in low-quality but mass produced isekai manga have made me go 'huh' more times than I'd like. It's just capitalizing on a popular trend in a sillier and less amusing way than other trends, but that's just for me, I suppose.

Otherwise, I think things are generally the same. I find manga from the 80s - 90s are some of the best in terms of quality, pacing, and plot but you can't find a lot of it in English. Then there was a period of time (looking back now; I can't say at the time I thought things were bad) in the early to mid 00s where there were powerhouse series but a lot of the other stuff doesn't hold up on re-read. So, I don't think we're getting any worse / I'm enjoying things any less.

There is definitely no improvement or decline in story quality, it just fit its time mmm...
But the drawing and paper quality definitely increasing so overall it's getting better mmm...
If you think it's declining in quality, it's because you remember some of those few great old manga, but you might not even realize there are tons of garbage in the past too mmm...

Because it became way easier to just draw something and put it out, average quality in general went down, but of course there are talented mangakas out there right now like there always were...

Manga, no. Anime, yes.

I think that there are so much more manga released to a much wider audience that there are bound to be more "bad" manga, and with the way social media works those bad manga get more attention...
For the 20+ years I've been reading manga I've always found bad stuff that I just couldn't continue reading.

In general, no, but some new manga are really bad.

There was always generic garbage and that hasn't really changed. From the old stuff usually only the best survive and sometimes some old manga that gets an adaptation or suits current tastes. I recently rediscovered "Shangri-La Frontier" which makes me keep my faith in the current gaming genre … but with the intense competition against comics, web-media, globalisation, if I hadn't found that series I'd be ranting about some atrocious works that see the light …

I thought there'd be more on the yes side. I mean there's always been a crackdown on scanations, but they're really going down hard on English ones and I do see a delay affecting even licensed releases outside the main magazines/series. There is also a surge on Spanish unlicensed / licensed translations, though that's more on the Korean/Chinese side.

In general, yes, but there are some really good works lately.

In general, no, but some new manga are really bad

imo this is a natural consequence of there being more/easier ways to publish these days. Digital-only publishing has a lower bar, so more stinkers sneak in. However, the baseline for a magazine is the same as it ever was, and a decent number of online works are still incredible, so to say that it's worse "in general" is just completely forgetting about decades of bad manga that no one even cared about. Mediocre-to-bad manga from the 1980s never even got translated so most of you guys have no idea how bad it was.

Survivorship bias makes it easy to remember older manga as "better" because the good (& the amazingly terrible) manga that we read then are the series that linger in our minds. I've read a ton of mediocre older manga over the years, none of which I could tell you anything about, because it was so forgettably dull that that left no impression in my brain.

Part of the problem is publishers opening the flood gates and funding way more manga and anime than they used to, so way more bad products get approved.

Another part is that, increasingly, authors don't understand how good literature works: they take the moments they like and reproduce them (sometimes with a spin) without actually knowing why something worked. This means all sorts of issues from plot contrivances to awful characterization, to edge for the sake of edge with no realistic filter.

Another part is that, increasingly, we're on screens and not living life. Miyazaki complained about animators not having enough IRL experiences to create something special and he's been proven right. The best stories seem to be from authors who know how people and places interact with each other. Kind of hard to avoid stereotypes and checklists when you don't know anything but.

I'm also starting to see a moral failing among some new authors (a different way manga overall may getting worse). For example: there's an isekai manga that wants the reader to cheer for rape.

Some publishing agent actually got this funded, apparently.

And no, seeing how bad it got wasn't worth it.