Superheroes in the US: Edgy and grimdark angst fest where no one is ever happy because drama, the continuity is a mess due to the 5 reboots that happen per year, where any hack can become a writer and half the time the art sucks dick

VS

Superheroes in Japan: Stories that reconstruct the hero's journey concept, extremely noblebright, filled with consistent plot and amazing art.

Isekai in Japan: OP Gary Stu that has no personality so that average Japanese man can insert themselves into him enters a world with the same videogame fantasyland look, builds a harem of cardboard chicks and maybe does some other dumb shit.

Isekai in the US: A character with a likable personality is inserted in a world with deep lore whose mysteries are explored, very unique and actually has dramatic tension.

Japan didn't invent the isekai genre; it's just their word for "portal fantasy", which has been popular in the west for far longer than it has been there.

If you want a cursed phrase in your head "The Wizard of Oz is an isekai" is a phrase that is technically correct.