IMO a lot of Bennett's problems have always been mental. He would get these amazing rushes in the playoffs and play with all the confidence in the world. Then he would get in massive ruts, and it went way beyond his own line mates. He would get low on himself and just play dumb. I really don't buy the "he didn't get a chance at centre" argument. Bennett is a professional, with experience playing at wing. Also, if you watch anyone who plays with Monahan/Gaudreau, they all play a hybrid role. Gaudreau and Monahan are not typical for their positions. When Lindholm was with them, many of his duties were those of the typical centreman, and the same happened with Bennett. When Bennett and Jankowski would play together, they would switch off centre duties, for eample, as to who was carrying the puck down the middle.
You can definitely fault Flames management for this too. They have a system in place where minutes have to be earned. This can obviously have negative affects on a player who psychologically gets down on themselves and needs to succeed to have confidence. There is major good and bad to this, but in the new NHL, where specialized skilled players are becoming dominant, this system may no longer make sense.
It's also an issue of Huberdeau and Barkov being the types of players who help their linemates excel. It's not just Bennett having a career level of play in Florida. Basically, anyone playing in the top six in Florida is putting up career numbers.