My main takeaway from Quantum Field theory in grad school was that the proton (and electron, etc really all subatomic particles) is just a useful fiction; much like a spherical, frictionless cow. It's just that in particle accelerators where it breaks down so it's a quite useful fiction. Renormalization[1] in field theory is really trippy...
[1] https://en.wikipedia.org/wiki/Renormalization