Additionally I think it's also just nostalgia and getting older. When I played rollercoaster tycoon when I was younger, the park guests felt alive, I didn't know everything that could be researched yet, and I didn't play to maximize the score. Now I know too much. The guests are just a simple algorithm, everything feels known, and I'm way more focused on actually playing for the objective. I still like RCT, but the magic from those days is gone. As we learn more about the world and get more responsibilities we seem to lose this sense of wonder about everything. Even new games often seem like something you already know, instead of something completely new, just because you've seen so many games already.

That being said, I can personally still get back to that feeling of wonder with the right games. It's not totally as it used to be, but there's still plenty of fun to be had. If I'm in a phase where I keep closing every game I start, I know I'm just not in the right place mentally and it's not because of the games.