This isn't unique to video games*. It can happen with anything that you spend a ton of time on, and either burn out on or start to develop more refined taste in. I've had it happen with:

novels
board games
movies
people

You start to see patterns, tropes, or just plain get burnt out on something. It's a sign you either need to take a break, or that your tastes have simply become refined enough that you require a higher bar to find something interesting.

I'm in my 40s and definitely don't play games as much as I used to. But there are still times I get sucked in and have a great time. Most recent example: Cosmoteer, a spaceship building game with loads of freedom and creativity. I'm also looking forward to the Factorio DLC and the Dyson Sphere Program combat update.

Edit: case in point that I can still get excited about games: I finally tried Shadows of Doubt and, wow, what an interesting game. It's like a Deus Ex shadowy sneak-around world with detailed voxel simulation.

* though the enshittification phenomenon is a real thing, and why people should play more indie games