Nostalgia I think is a big part of it. Plus, I might not be part of the target market these days. I have a 16 year old nephew and we tend to discuss games. He only plays the new stuff and I don't. I have seen this with some people who, for instance, can't watch black and white cinema, no matter how good it is.
Another part of the allure of older games is simplicity. Big productions are too cumbersome and designed too safe these days. When games were made by small teams there was more originality. If you need a palate cleanser, you need something fresh and original, not another 3rd person action game like a thousand others.
Another are the origins. If you go back and see an evolution of computer game design, from mainframe computers and electromechanical games you tend to enjoy the artistic and technological progress, from Zork, Black Onyx and Xevious to Disco Elysium, Baldur's Gate 3 and STALKER 2.
I used to think I mostly preferred older games. However, I recently tried to think of which were my favourite games, the ones I liked the most, and my favourites were usually made in the last ten years. That, in a way, is reassuring. Old games are limited because I can only play what has been made. But if I can still enjoy new games then I can still look forward to new games that haven't been made yet.
In the end though, while the ones that have enraptured me the most are recent, I tend to play, for fun, mostly older games.