Newton just came into the NFL at the wrong time.
A few months ago I was listening to Felger and Mazz and Felger said one thing that was correct and then followed it up with one thing that wasn't. First, he stated that Newton will forever be labeled as a "quitter" for not jumping on the fumble in the Super Bowl. He said, rightly or wrongly, that his failure on that play cemented his reputation as a quarterback that can't be trusted to do the things necessary to win. To add to this, his reputation had already been that of a showboat and selfish guy, due to prior comments that he'd made, to the Superman stuff, and due his larger-than-life personality.
A couple weeks later, when the subject of racism regarding Newton's failure to land a job in the offseason came up, Felger pointed to the big money deals for Mahomes and Wilson as evidence that the league doesn't care about a quarterback's race, so Newton can't use race as an excuse. What he failed to acknowledge, in my opinion, was the changing NFL landscape between 2011 and today. Newton came into the league at a time when being big (both physically and personality-wise) and Black and a quarterback was not entirely acceptable and subsequently developed a reputation based upon unfair criticism as well as some mistakes that he made. Once his reputation was cemented, then he couldn't shake it, regardless as to whether it was true. I've heard he's "a "me" guy, can't read the playbook, lazy, "acts like he's bigger than the team" and my personal favorite "isn't tough enough" a million times. All these criticisms are baked into his reputation that was developed before the emergence of the new wave of black quarterbacks in the league. Fortunately we now live in an era where Newton's present (and past) behavior is more widely accepted. In my opinion, if Newton came out in the draft next year and behaved the same way, his behaviors wouldn't be viewed so negatively.
Newton has obvious flaws. But for this guy who dragged an inferior team to a Super Bowl in 2015, at the age of 31, to spend 89 days unemployed when a bunch of inferior players were getting higher paying jobs was a joke. I think that is obvious now. Just like Kaepernick not getting a job. And I can't conceive of another plausible explanation for it other than what I described.