I'd say I am tired of new games in general. I cannot quite put my finger on what I dislike in them, but something feels off. While I liked Witcher 3, somehow it didn't give me the satisfaction KotoR gives with each replay. Starcraft 2 campaigns were awesome, but Warcraft 3 campaigns felt more... "right" to me? Battlefield 3 was incredibly well made, but old good Doom still gives me way more enjoyment.
I think it is something about old games being simpler, having clearer rules. Sure, Neverwinter Nights or Baldur's Gate 2 might seem complicated on paper, but it doesn't take too long to learn all the things you need to know to effectively play the game. The map design is very simple; in fact, you can easily replicate most design elements in the NWN toolset. Everything is built in very simple and easy to figure out ways. Compare it to, say, Dragon Age: Inquisition with its combat with many "degrees of freedom", with each location having so many elements in it, with each rock looking uniquely, with complex dialogue animations... I used to adore the things the technology can do, but I think nowadays too much is put into technology and too little into making do with what little you have to create incredibly fun games people would play for decades. People don't play to this day Doom, Neverwinter Nights, Age of Empires 2 because those games are technologically great by modern standards, they play them because the developers managed to create brilliant games with simple low-tech tools.
Honestly, I even find some older games better looking than modern games. Doom 2 might have had a very low graphic fidelity, but it is the simplicity of the graphics that makes it look somehow warm and cozy even today (at least, with high-res mods). While Witcher 3 has brilliant top notch graphics, but, due to the complexity of models, things look somehow alien, unnatural. Made not by common folk but by some special researchers in a secret lab.
Bottom line: I must be a conservative that likes the old and dislikes the new, but I find myself going back to old games (mainly made in 1993-2003) more and more often. I bought an insanely high tech machine to play modern games at ultra settings at 4K, and after a few months of initial excitement I play games on this machine my business laptop could easily handle. 