Aye, I think you'll find that lots of us understand this one.
I'm 37. And I'm male. But when it comes to my interests? I couldnt give less of a crap.
Lemme show you something: https://pre00.deviantart.net/b405/th/pr ... 9juchu.png
Have a look at that. That is Kirlia, from the Pokemon series of games. I love Kirlia. It's so... freaking... cute. I like it so much, I bought a plush doll of it. Why? Because I freaking wanted one, that's why. Does this look like something a 37-year old male would have? Probably not. Do I give a fart? Nope.
It's the same for all of my interests. Video games are my main thing, twisty puzzles are another one, and I'm very into cosplay as well. Granted, video games in particular have been much more accepted among many age groups as of late, but still. It's *the* hobby for me. But the other ones... if you dont know what "cosplay" is, it's the act of dressing up, in costume, as some favorite character from... whatever. In my case, it's characters from games (usually feminine or androgynous characters, too, because I freaking can), but it could be anime or TV shows or whatever. This is typically done at conventions. To some, this might seem like a silly thing. But to me? I'll do as I like, thanks. And I quickly found that at a convention, everyone else tends to think the same way. I learned that it's not just me with my autism that does the things I do: Plenty of otherwise "normal" people get MUCH more "weird" than I do, or have similar interests.
You worry about maturity, but... well, I'll put it this way. My definition of maturity is simple: The ability to make my OWN decisions. Instead of worrying about what others think, I'll buy the freaking doll if I want the freaking doll (I also have LOTS of other figures and things, too. Heck, I've got really BIG plush figures from freaking Minecraft, because I happen to like Minecraft, and to heck with anyone else if they have a problem with that). I'm a mature adult: I CAN DO THAT, I can buy those if I want, so I will.... simple as that. That, to me, is actual maturity. I dont see the need to "prove" anything to anyone.
I dont exactly bother keeping any of this private, either. I really just say.... "bah".
If the people around you are acting badly towards you due to this... then maybe you've surrounded yourself with, well, idiots. Anyone that could be a real friend towards you, wouldnt be acting like that just because of those things. Look for others with similar interests instead. Believe me, they're out there, regardless of age.