I've seen the mess that was the BTS stuff and all that, as well as some great ideas other people had for the movie.
–The Furious Five and Shifu were taken out by Chameleon and had their powers stolen, and she does the same to Tai Lung and other masters. But Tai Lung manages to escape and has to team up with Po in order to stop her. He's not exactly a paragon, but he's mellowed out over the years and eventually fully redeems himself.
–Zhen being a persona invented by Chameleon and it being a way to put Po on a fake hero's journey in order to take his powers and replace him as the Dragon Warrior.
–Po's birth dad being forced to face his fears and overcome his trauma when facing Chameleon currently using the form of Lord Shen.
Tl;DR: Mike Mitchell shouldn't have been the co-director, Joel Crawford should have replaced him but goddamn I wish Stephanie Stine stayed as director.