When I learned about causal sets program and algebraic quantum field theory, I finally (somewhat) understood quantum physics.

Tl;dr spacetime does not exist as a global background where things are "placed", it is not ontic. "Things" are first, and spacetime is derived from interaction statistics of "things". This eliminates nearly all naive paradoxes like double slit etc. Now, these "things" are somewhat complicated and non-intuitive (e.g. there are no individual "particles", they are a limit of discrete distributions), but that's a good start.

Sorkin is great. I think causal sets make some things simpler but other more mysterious. I also found t’ Hooft’s automata and Spekkens toy illuminating in different ways.

"Was", unfortunately. He died this September. What a loss, he earned a Nobel long ago.

I am so sorry to hear this. I enjoyed visiting his web page July, when I came upon a couple of emails he had there, which were eye opening as they made some of the philosophical thoughts behind causal sets much clearer. A huge loss, but he did contribute amazing work.