There are 2 currently, and they don’t mix but so what? Who says they should fit each other. I get you. In one situation one set of laws wins, in another the other does. Just like jurisdiction in criminal laws and rules in languages. Scientists are intent on reductionalism at all costs but the Universe may not be that simple. And it evidently isn’t.

Relativity v quantum mechanics – the battle for the universe

Link: https://www.theguardian.com/news

Physicists have spent decades trying to reconcile two very different theories. But is a winner about to emerge – and transform our understanding of everything from time to gravity?