The game table can be a lonely place. Everyone else is running around, having fun exploring their pet plots or doing cool things, but no one seems to be interested in the thing you want to do. So you sit quietly and wait, and you get more detached and disinterested in the game. You drop out.
The bigger the group the more this happens. It’s an inescapable mathematical rule that more players means less play time per person.
So how can you salvage things? You need to find a partner in crime, someone else at the table who’s willing to do the thing you want to do or talk about the thing you want to talk about. Two players working together have more influence over the game than two players flying solo, and even if you don’t get to do everything you want you’ve got some company and moral support. A co-conspirator makes any game more fun.
Look around the table. See another player checking out? That’s could be your partner in crime. They may even need a buddy more than you do, so do them a favor and team up.
A good partnership requires compromise and reciprocity: if they do what you’re interested in, you should also push for what they’re interested in. Sometimes it isn’t even an issue — lots of players are flexible about what they do so long as they get to do something. It’s more about having a voice and participating than pushing any particular agenda.
If you’re playing something story gamey, even agreeing to be adversaries can be teaming up — you’re cooperating in bringing your conflict front and center.
GMs, same advice: look for orphaned players and try to hook them up with someone else. If you have a large group (by which I mean even 5 players in a roleplay-heavy game) start people off in pairs or sets. Never leave a man behind.