I just finished playing the original FF7 for the first time in like two decades. I always secretly dreaded trying to play it again, worried that it wouldn't have aged that well as a game, or that my nostalgia was propping it up as a masterpiece when perhaps it wasn't.
It sucked me in and I ended up doing a 100% completion playthrough. The experience has shifted my thinking and now I'm more willing to replay older games. Just last week I found my old CD Keys and started up Diablo 2, the original, not the remaster. Now I've been sucked into that.
I personally am finding that mechanically, these older games have systems with lots of depth and creativity. They give you so many options and choices, and they rarely explain all of it so your kind of left to just.. experience it. I am sure this is not true for every retro game ( and ditto for some new games ) but it is something I have been feeling when playing older games.