For my part I was disappointed in Morris early on as our defense was not as great as the previous year. It was a fair expectation to be close to where we were last season. I was down on him but didn't want to see him fired as a few other guys felt. OTOH, they were venting their frustration and that is understandable. But firing would have been too drastic a move.
Morris could NOT have invented an entirely new scheme mid-season. Much of what he was doing began to work. Football is a game of inches and minor tweeks to a defensive scheme, and addition of new personnel, can have an important impact.
At this point I don't think that anybody can throw shade at Morris. I wouldn't use the term "haters" because it is really a pejorative, and I think those that wanted him fired would freely admit they were wrong. This is just another disagreement about shades of grey, similar to, "who should have been the game's MVP?" or "what was the key play?" etc.