Doesn't the fact that both General Relativity and Quantum Mechanics don't make correct predictions at all scales already show we're fundamentally wrong?
Maybe. Maybe not. There might not be a Universal Theory of Everything. Everyone hopes there's something and most scientists do believe that something is out there, but the idea that there might be reasons we can't unify them or that there are physical limits that prevent us from gathering the information we need to fully suss things out isn't exactly fringe science.