I think that Walters main problem is that he's too slow to react to things that need changing. I think that part of this is his lack of head coaching experience, and his desire to appear like a nice guy. He was behind the 8-ball ever since his late hire trying to do a large number of things that needed doing simultaneously. I believe that he saw what was necessary and did them (e.g. hiring staff, getting QB, alumni donations). I think that he did the best that he could do, it's unfortunate that some of the personnel he had better hopes for haven't fulfilled their functions. What's bad is his slow reaction to change what needs changing. It's been apparent to many posters here for a long time, but he basically changes nothing until he he's forced to. Like the lack of ability for the offense to get a few yards on needed short plays, just run it again and fail again.
He's finally come to see that his defense needed to be changed and did it this week. But the offense remains offensive. Certainly the OC's downward career trajectory and his lack of making adjustments during games or during the season suggests that he needs to be replaced.
But Walters needs to make critical decisions more rapidly, if you don't make them in a timely fashion you lose while playing games, and also lose future unplayed games. He's done things to enhance the program's distant future such as new uniforms to give an easily recognizable Purdue identity, trying to start a new tradition, driving a spike after a win. But he needs to react more quickly to change things that need changing, but it may be too late for that. We need W's, otherwise, Purdue football will continue to regress.