I think the frustration is that Tom Brady was everything Mac Jones is not. It's a very noticeable drop off. You go from the penthouse to the outhouse seto speak.
You get accustomed to the comebacks, making everyone else better, championships, & GOAT performances. Then, one day it's suddenly gone. Instead of being conditioned to a win when your QB has the ball late, you go to expecting a loss in the same situation.
No matter who it was, the next guy at QB walked into an impossible situation. I think if Mac had been drafted a few years after Brady left, it may not be as noticeable. But he was drafted a year after Brady left for Tampa.
So I do feel bad for him. Unfortunately, it appears as though an amicable split may be beneficial to the organization and Mac.
I should add..the HC did him no favors by sticking him with Patricia and no great #1 WR/good OL.