QM was developped to answer the issue of electrons spiralling out of atoms and being extremely short lived according to Maxwell equations.
Thus, its maunly a theory of compatibility of atom with EM waves, which means that other aspects of the system like gravity, thermal, Lorentzian Mechanics etc were simply rendered peripheral.
This has not however been argued sufficiently. Therefore, QM is mainly a enforcer of an ad hoc chosen aspect of nature and not so spherical in motivation.