Due to the nature of the sport, football has a significantly higher risk of CTE than MMA does, at least based on our current level of understanding. MMA is actually relatively safe, interestingly enough.
Football has to change to respond to the brain injury thing. It just has to, in the same way it had to change in the leather helmet days before the forward pass when college kids were literally dying every year. But that's entirely separate from Listenbees "oh boo hoo they made me rehab my injury" complaints. It stinks that's he got injured, it stinks that his NFL career might have been stunted, but outside maybe some injury insurance I don't think that's gonna be where football sees the necessary long term changes.