I understand where you're coming from.But maybe this will make you feel better if you look at it this way.
Deangelo was drafted in 06 and is still productive in the league. Stewart 2 years after him and still a huddle favorite. So those 2 kind of go against points 1 and 2 that you made.
3. Injury concern is valid and a higher risk but as we saw with Benjamin and Butler early, injuries can happen at any position.
4. The common denominator in consistent playoff teams is there head coach and QB combo. Steelers and Seahawks have always boasted a good run game a defense in their most consistent years and those pop in to mind immediately. Sure there's more.
5. I don't think it's fair to worry about Fournettes 2nd contract when we have him for 4 years under a rookie deal and a 5th year option that will be reasonable as well.