That has been one of my concerns as well. Yes, GamePass has a LOT of games to play. But does it have the games I want to play?
I pay $180 per year for GamePass, but then I still have to buy Assassin Creed Valhalla, Immortal Fenyx Rising, Demon's Souls, Spider-Man, Cyberpunk 2077, Control UE, Hitman 3, RDR2, etc., when they release.
If I purchase them, my gaming budget goes berserk. If I don't purchase them, I'll be filling my time with games that I don't really want to play. That's a double-edged sword. I'm glad GamePass is working so well for so many gamers, but I haven't been able to get past this problem yet.