Yeah I think a studio is fine. It's still living on your own and paying for your own place. Don't see how any extra bedroom or two makes any difference. I mean if you were going from renting a studio -> buying a house that would be a nice step up and owning your own place has a lot of advantages (though it doesn't have anything to do with being "grown up"). But yeah, if you don't need the room, and can't easily afford something better, then what's the rush?
Like for me, I'd like to have a house someday just to not have wall-touching neighbors so I can blast music/movies/games at 3am and never care. Would be nice to have a yard to like try gardening or something. But realistically it's stupid because I don't need the space and it'd be tough for me financially, so I'm gonna wait until I'm in a long-term relationship with someone who has a 2nd income, which might be like in my 40s or 50s or maybe never, but who cares.