Quantum mechanics is fully unified with special relativity, and has a clear concept of spacetime. The Dirac equation was discovered in 1928 and was the key to solving this problem. This means that quantum mechanics is fully compatible with time dilation at large speeds, that it respects the limits of the speed of light (current article notwithstanding) etc.

The only incompatibility is between quantum mechanics and general relativity - quantum mechanics can't work with the general relativityequations for a curved spacetime or for the gravitational effects of particles being in multiple places at once. These are the things that a theory of quantum gravity must solve.