Quantum mechanics didn't supersede electromagnetism. Again, they're different things. Electromagnetism is a fundamental interaction. Whereas quantum mechanics describes the mechanics of quantum particles. Whether those particles are affected by electromagnetic forces or not. It's a description of how they behave at quantum scales.

Coulomb's law has nothing to do with quantum mechanics, it's a description of how macroscopic charged particles interact. What the OP should have said to be correct is:

Awesome to see the similarities between: Newton's law of gravitation and Coulomb's law

I don't know where he got quantum mechanics from.