I know what you mean.  A lot of the user base here are just kids, at whatever age, but there are a good number of older writers and just good ass writers.  You definitely have to kind of suss out who is who but there are plenty of folks.

Sites not dead but it has lost a ton of users and a lot of the users still here don't actually RP anymore.  Many reasons for that, none of them likely to change anytime in the foreseeable future, IMO.

Saw your intro post.  I feel similarly about High School and College RPs.  You seem to have an interest in comics.  Maybe check out...

https://www.roleplayerguild.com/topics/188543-marvel-comics-dawn-of-x/ooc

There are several RPs and several RPers who pretty consistently put out good stuff, depending on what kind of RP you like to do.

I'd suggest JB, Ruby, Hellion, Penny, TGM or maybe TMG I always forget, and Poohead.  Just as sort of starting places.

JB does a lot of Warhammer related stuff
Ruby used to be an admin/mod and does some good ass superhero RPs.  She's the GM for that RP I posted a link for.
Hellion is an old friend and does some really good RPs in several genres.  Some fantasy and a lot of cyberpunk.
Penny I don't know her proclivities but she writes a good deal at high quality and has for forever.
TGM/TMG does superhero RPs sometimes including my personal favorite 1968.
Poohead does a lot of fantasy stuff and is a [b]straight up[/b] published author.

All of these folks are in their Late 20s to Early 30s.  I think most are early 30s.

I'm in my mid 30s too.

Bounce, Hound55, and BruceWayne all make really good Superhero RPs if you're feeling like one of those too.  I don't believe they currently have one active but look them up.  Not sure how old they are but top notch writing.