As people are getting more atomized they interact with fewer people. This is why I think step-whatever and teacher stuff is so popular right now, the idea of meeting new people is getting increasingly alien to a subset of the population.
That subset is also very invested in any way to distract themselves and escape that existence, hence why there is so much media catered to them.
I can tell that I'm starting to get old when I think of 20 year old anime as fairly recent. But alienation and atomization didn't begin in the last 5 years, it has been a long process.
You can also tell the way that things are starting to turn less grand on possibilities. The recent glut of isekai anime is a perfect example as you would have isekai before, but now they tend to all be based on online games. That is where viewers can imagine themselves in the shoes of the protagonist.
Isekai anime are stories where a person is transported from the normal world into a fantasy one, where they are often incredibly powerful and have many girlfriends
That goes pretty far back. Chronicles of Narnia is that without the girlfriends. Alice in Wonderland, The Phantom Tollbooth, Monster Rancher, The Cheetahmen game on the action 52 cartridge etc.
Yeah, but you're talking about decades between new stories. Today it's like 3 out of every 4 anime released in a season are Isekais and the fourth one is a medieval European fantasy setting with rpg mechanics.