I don't think Einstein rejected quantum mechanics. Like many smart people trained well in classical physics, he was skeptical of many conclusions regarding determinism and information that you could draw from the math of QM. He proposed experiments to try and disprove certain things like a good scientist.

Fun meme though :)

A lot of people heard both of his opinions, but a lot of things happened in between, so this is expected.

Bra-ket notation is beautiful