have you ever considered that it might be the other way around - that people like things that are targeted at their own generation?
take the progression of the harem anime evolution for example
back when millenials were horny teens, the harem genre focused on the ideal of latent potential
. Our protagonist actually had some hidden talent all along, or he was actually a really awesome person that no one had realized until beforehand. This kind of idea resonates well with the millenial generation, which typically views themselves as unacknowledged geniuses who would totally be popular if the world understood the truth about them.
now that the kohais are horny teens, the harem genre focuses more on escape
and new powers
. Thus the isekai boom, this is a convenient setting for these ideals. the kohai generation typically likes these because they believe the world is headed for bad times and it would be nice to go somewhere else and get cool new abilities to make life easy.
but just becausesomething is marketed at a certain generation doesn't mean that other generations can't appreciate it if it's good. like believe it or not, I am not the person who constantly complains about tubers and although they're not my favorite thing i do like to occasionally watch them
so yeah in conclusion I don't think it's fair to say that people are necessarily picking their likes and dislikes purely on whether or not it relates to their generation, but ratehr that media marketed towards their generation is naturally going to appeal to them more because it's what they understand.