Some of it can be age related in a number of small ways that add up: nostalgia is the obvious one (and others have mentioned), but there are all the little bits of things that add up to change what you can spend time and attention on. When you are in your early teens with "not a care in the world" it's very easy to deeply immerse yourself in a work, but as you grow older you gain responsibilities and cares and can't afford to spend as much time or attention.<p>Immersion requires you to spend time and attention. To some extent immersion is a sensation of attention grabbed with time slipping away. To be immersed, almost by definition, you need to give the game your full and almost undivided attention, and be able to let time flow freely without notice. That can undoubtedly get harder as you age and get more things demanding that you spend time or attention on them; more things demanding you box your time or your attention means less opportunity for play, for immersion.<p>Nostalgia plays into it because you become more willing to shuffle your time and attention around for things that your brain already knows it can enjoy. New things are a risk and if you are already so aware of how many things require your time and attention, it can be tough to take that risk on something new. There's a Catch-22 there as well that because you feel you are gambling by playing a new game, if you set immersion as your quality bar, you'll never reach it because the gambling instinct to hedge your bets against "heartbreak" hedges your time and attention from even being able to reach some of those levels necessary for immersion (thus almost guaranteeing "heartbreak" by trying to avoid it).<p>Beyond time and attention there are a lot of aesthetic and subjective factors you can explore. It is quite possible that, for instance, you prefer the lack of graphics detail because you can fill in the details with imagination. Obviously there are people that will always love books more than films, but those same people can still enjoy a good film and kind find things to love in cinematic arts. The more you can figure out what it is subjectively that you love in older games, the easier it can be to find the parts of new games that cater to your aesthetic or even entire new games built specifically for your aesthetic. (Circling back around, the more that you can find things that are flavored in a way that meets your subjective desires, the easier it becomes to spend time and attention on them and thus find yourself immersed.)