I'm looking for good mecha manga or maybe anime (i know this is manga forum) preferably without angst teenager riding some random op mecha that's appear out of nowhere and can ride it instantly without even learn how to do it.
If just ginga eiyuu densetsu have mecha it would be great.

Anime:
FLAG (I haven't finished it yet but it's fairly down to earth)
Armored Trooper Votoms (I recommend the TV series but not all the OVAs are good)
The Big O
Patlabor (The OVAs, movies, and TV show)
Tengen Toppa Gurren Lagann
SSSS.Gridman (More of a giant hero show than mecha)
SSSS.Dynazenon
Dragon's Heaven
Shin Getter Robo vs Neo Getter Robo (You should read Getter Robo beforehand)

I'd also recommend most of the universal century Gundam entries, but they tend to have some teenage angst.

Manga:
Getter Robo + its sequels
Appleseed
The Five Star Stories (I haven't read it yet but it's supposedly a space opera similar to LOGH)
Joshi Kouhei
All You Need Is Kill

If you'd like series which don't necessarily have mecha but involve machinery, I'd recommend:
Blame! + Nihei's other work
Ghost in the Shell + it's anime adaptations
Roujin Z (anime)
Robot Carnival (anime)
Manie-Manie: Meikyuu Monogatari (anime; only one section of this anthology film focuses on robots)

Quote from saltylettuce

Anime:
FLAG (I haven't finished it yet but it's fairly down to earth)
Armored Trooper Votoms (I recommend the TV series but not all the OVAs are good)
The Big O
Patlabor (The OVAs, movies, and TV show)
Tengen Toppa Gurren Lagann
SSSS.Gridman (More of a giant hero show than mecha)
SSSS.Dynazenon
Dragon's Heaven
Shin Getter Robo vs Neo Getter Robo (You should read Getter Robo beforehand)

I'd also recommend most of the universal century Gundam entries, but they tend to have some teenage angst.

Manga:
Getter Robo + its sequels
Appleseed
The Five Star Stories (I haven't read it yet but it's supposedly a space opera similar to LOGH)
Joshi Kouhei
All You Need Is Kill

If you'd like series which don't necessarily have mecha but involve machinery, I'd recommend:
Blame! + Nihei's other work
Ghost in the Shell + it's anime adaptations
Roujin Z (anime)
Robot Carnival (anime)
Manie-Manie: Meikyuu Monogatari (anime; only one section of this anthology film focuses on robots)

Thanks for this great recommendation list

That's a great recommendation list thanks!

These days mecha themed seems declining meanwhile isekai themed become even more popular than ever, it's funny in the past we got a lot more mecha or sci-fi series like astro boy or getter robo. But now in the future we back to the past playing with sword and magic 🙄