In my dotage, I find that it's better to just roll with it (heh).
I do have preferences. But my preferences tend to moderation. For example, I dislike games that are just one combat after another, because I prefer role-playing. But I would also be sad if there wasn't combat, because I enjoy playing "hit them, then hit them again" characters.
It's been my experience that if I relax and try to enjoy a group for what it is when I'm playing*, instead of carrying in my own expectations, I have fun.
That said, I don't have fun if a group is excessively rude, mean to each other, or is just about PvP (in terms of killing each other- some friction from roleplaying is fun).
*Necessary disclaimer- I have spent the vast majority of my time DMing. So, really, any time I play is a bonus.
I'm not very old, but I've often lives in areas with low levels of gamers, so much like you, I'll usually take what I can get.
Almost any system for building characters is acceptable. Okay so I can't make a half-dragon, half-vampire, half-wendiigo in this game, and we all have to be humans, eh, whatever. Very rules heavy, not-very-rules-heavy doesn't bother me. As long as I understand that from the outset, I'm good.
Here's some things that just
bother me, but aren't deal breakers.
Unknown advancement system. Bob just earned a level for killing the princess? Joe just earned half a level for killing a demon, Sue just got 10 XP for routing the theives guild? I'm confused guys. I like there being a clear metric for achievements, or at least a regular advancement over time (in or out of game) if we're not using XP.
Overly-talkative DMs. I get telling a story, I do, but sometimes a DM just goes on and on about all the little details. I get it, it's pretty. But if it's not really relevant, just tell us "it's very beautiful".
Games that don't encourage us to be a party. It's fine that every character has an agenda, and it's fine to allow everyone time when available to advance their agenda. But the DM should make some effort to tie those agendas together in the background.
I do have a few deal breakers, but they're more to do with the people than the game.
Rude/Mean people. Should be obvious. I can tolerate a little gruffness, it happens. But I have no desire to play with jerks.
People with unclear schedules. If you let me/the DM know in advance you can't make it, or need to leave early tonight, that's fine. But I hate finding out half-way through the game that your mom called and you need to go feed the goats RIGHT NOW. We're all here to play and you're an adult, even if you're living at home.
Encouraging PVP. I don't like fighting with the party. I
will if I have no choice, but typically I'm not interested in doing so. It never works out well.
Non-con. Rape happens, bad sexual things happen. It doesn't need to
not exist to make me happy, but it doesn't need to be front and center either and I will walk the moment you non-con a player and I do mean
that moment.