I actually don't think Fields and Trubisky are that similar. Trubisky struggled to move past his first read, and he had those weird issues of being able to pass to one side of the field. Fields struggles to make accurate reads, which is different from sticking on your priority target.
It's more that "Wait till he gets to a new team and new coach, then he'll show all the haters" is just part of the standard NFL QB bust stages of grief. The NFL brings in an average of 3 new first-round QBs per year and another 8-12 in subsequent rounds.
That's a whole lot of busts floating around, and the vast majority of them are never going to get a second wind of success with a new team. For every Tannehill, there's a lot more Blaine Gabberts, Jake Lockers, EJ Manuels and Josh Rosens.