Classmate wa Isekai de Yuusha ni Natta kedo, Ore dake Gendai Nihon ni Okizari ni Narimashita - Vol. 1 Ch. 1

[Sunspawn]

It's kinda sad that the level of originality in manga has dropped this low...

"Here's an isekai concept"
cue a hundred copies
"Oh, that's old now?"
"Here's a different spin on the last isekai concept"
cue a hundred copies
"Here's a slightly different spin on the different spins found in the isekai genre"

Honestly, every category of everything seems to suffer from this but why does it feel so pronounced with isekai?

Because the baseline concept of the genre is basically "virgin isekai vs chad fantasy".