I disagree that a magical and not explained force at a distance (Newtonian gravitation) is a physical cause.
May be you got one apple to much on your had...
A physical cause is per definition something you can measure in reality. As a such gravity is very real. QM is just an engineering framework to map potentials. Based on a very good base measurement you can make approximative calculation how unperturbed potentials are distributed. QM alone has no value at all like a sheet music you need an instrument = base measurement to get something useful out of it.
Unluckily QM only works for conservative particles/forces due to it's restricted math. QM already fails for hydrogen as it does not model the 1/r3 magnetic "electron potential interaction" that behind the scene changes the Coulomb potential function.
QM/QFT never worked for anything except when tons of fudging factors where used. It's famous predictions were based on a few excellent measurements, where on the 1 bit x 1 bit x 1 bit permutations rules were applied...
We still wait for THH to present us the marvelous QM/QFT formula for the up quark that exist about 1024 times in one gram of Hydrogen... My be he could start with the down quark that is known with a little more than 2 bit precision what means you can choose one apple out of 5...