There is a 3rd part to this that is very rarely discussed. His "Jones fracture" injury. There was quite a bit of discussion about it when the injury occurred and whether or not he would ever be the same player again. It is true that most do return to the same level of production after that type of injury but not all are able to. We talk about "he got paid and doesn't care" or whatnot, but that injury happened 2 games into his new contract. Unfortunate timing but it is what it is.
Now don't get me wrong I am not blaming it all on the injury. He was never a great route runner, and Romo was able to make him a better receiver because of his accuracy. But I find the timing of the injury and the difference in the 3 years before it and 3 years after it to be very striking. 3 years before the injury: 273 catches, 3,935 yards, and 41 TDs. 3 years after it: 150 catches, 2,035 yards, and 17 TDs.
His best trait was the jump ball, if he was unable to recover, this got taken away (at least the consistency). He was unable to compensate because he of a few things (most on him): 1) He was never an accomplished route runner to begin with, 2) He refused to believe his skills diminished because of age and the injury, and 3) He refused to work on improving his route running because he still believed his skill set had changed.
This is all my opinion of course, but he simply was not the same player after that fracture. Sure there were other factors (that have been discussed ad nauseam for at least a year), but this was the starting point of the decline. While I agreed with decision to release him, it saddens me to see the level of vitriol he has been getting as if he hadn't put up possibly the best 3 year window of any receiver in Cowboys history or genuinely cared about and was proud of being a member of this team.