1. I understand software better and can see that my in-game actions are mostly changing variables, or values in a database.
2. Games are 'balanced' and therefore limit the upside for a potential great strategy I might come up with.
3. Nothing new under the sun: How many more pseudo-scifi research trees or weapon mechanisms or unit capabilities am I supposed to learn in my lifetime?
4. They don't make them like they used to. Older games had a hardcore element to them, were often quite difficult and unforgiving (a result of less market pressure and less polish). Instead of online guides and pro streamers showing how they are played, the games had a mystery about them; we often didn't even have a manual for a game we copied.
4. Less need to prove myself in competition with my peers through games and play (which is aparently a fundamental thing for children)
5. Less magic: The first game that had real voice actors, the first real 3D game seem to have had a greater impact than today's incremental improvements.
6. Limited time and energy. I find it tough to spend the prime energy of a day for a game.
7. Computer work makes me want to get away from computers eventually.
I do watch streamers and youtube videos of the games of the 90ies occasionally and find entertainment and closure (through experiencing games I never got to play).