One game that I’ve played that claims to be OSR, but isn’t, would be the Black Hack set of games. I’ve played The Anime Hack.
It’s like that joke about your grandpa’s old axe. Years ago the handle was replaced. Last year, you replaced the head. But, you still call it your grandpa‘s axe.
Once you’ve changed the majority of D&D rules, is it D&D anymore? I’ll be the first to say that it’s tough to know. It’s a subjective thing, as changing even one bit of the rules means it’s not the same anymore.