Good take. It’s really the only thing that can explain his drop of level from 22 to 24. injuries and surgery affected him and set him back, yes, and loss of two preseasons in a row didn’t help him, but his ball control, shooting and passing technique used to be much better. That stuff don’t disappear the same way. Also every coach around him has said his dedication in training has been top notch all this time.
So it’s confidence. Like you say, failing the pressures put on himself by himself and others, takes the joy and confidence out of his football. Ironically if a humble person is subjected to too much critique, it may spill over and result in pent up anger. When you see a guy like Rashford, always known to be humble off the pitch, shout back at fans criticizing him in a moment of failure - that’s not typical arrogance, it’s a typical reaction to critique heaped on top of mountains of self critique.
If Rashford comes back to his best, it will be because he is supported to get back to the fun of improving and succeeding with plays, and forget what anyone else might think he should or should not be.