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.
Oh yeah, i love greed island. It being an arc certainly keeps the novelty of the other world's mechanics from getting old.
To make it work as a full series you gotta have a lot more substance though, because at some point that novelty will inevitably run out. And now instead of "exciting new world where everything is different", it's just a regular world we're already used to. At that point you gotta have an actual compelling story to keep it going.