My answer to the OP is really "I don't care much about the system": I'm interested or not in a game based on what the game is about, who wrote it, what setting it's in, what kind of character you play, etc... to some degree, I might care about the system in terms of "what kind of system is it". Is it a modified 5e game? Is it inspired my MERP or by old-school WFRP? Is it a hack of some other system?
But really I tend to think about it more in similar terms as board games. Every board game has different rules: picking up a new board game means you'll have to learn it! So am I going to only pick Carcassone extensions ("it's Carcassone, but with space settlements on asteroids!") the same way I might only play 5e games? Or am I open to any board game except a few that have mechanics I don't like (say, I don't want to play deck-building games) ?
There's a couple decent reasons to not want or be able to play games using a new rule system. "Not wanting to learn something new" is not one of those in my opinion.
I need to sit and think for a bit about how board games =/= role-playing games; I mean beyond the fiddly bits and the board itself. But I strongly believe they are different, and it's not equivalent in terms of reading the rules.
Maybe the first thing on this I'll say before is that with RPGs, at least ones that are GM-ful, is that the GM is expected to know most/all the rules; while the players are not actually expected to know them at all to start. Board games are usually - let's open the game together and learn the rules as we go.