is sdl2 really that bad?

It's impossible to know what issues they have, since they don't specify.

But no, for the vast majority of people, SDL2 is perfectly fine, although SDL3 is a vast improvement. It's as stable and battle-tested as a cross platform multimedia library is bound to get. Opening a window and polling input is trivial.

Then again I've never even heard of the language they're using (Odin) so maybe that doesn't play well with a C library.