Heinicke is a good guy, but he is very limited as an NFL QB physically and mentally. He's very small with a very weak and inaccurate arm. Also, he doesn't see open receivers (or lurking defenders) and he doesn't throw receivers open.
Unfortunately, because of the O-line's inability to protect the QB, Wentz would do even worse. He is like a deer in headlights when he is pressured at all. He actually makes a mediocre O-line look worse. Wentz would need the 1991 Hogs blocking for him in order for him to succeed.