Yeah it was fun in the beginning, after all who never thought about being transported to another world where you ate a big hero with swords and magic?
But what the hell, I'm pretty sure there's more isekai now than other genres/settings. It's gotten to a point that if I see the tag I just move on.
Isekai is more of a setup than an actual genre.
If they weren't isekai, they'd just be shitty fantasy. Isekai allows writers to skip a bunch of steps and start with a fully-formed character the audience can relate to.
Hitchhiker's Guide to the Galaxy is an Isekai