I defend Dez because I think the criticism is exceesive. It's not like he doesn't need to improve. But there are mitigating factors to his "decline" in performance - namely the decline in play from the QB position almost from the moment he signed his new contract. To ignore that and assume it is ALL due to Dez is unfair criticism.
Now if, for whatever reason, Dak proves to gain more on-field chemistry with other receivers, and never gets there with Dez, that's a tragedy. And if that's the case, the team must choose to either move on from Dez, or upgrade from Dak. That's obvious. But it still doesn't follow that the blame falls completely on Dez. I think with the right QB, he's just as good now as he was with Romo. I really do believe that.
I'm rooting for Dak and Dez to figure it out together. I'm not anit-Dez or anti-Dak. But the blame lands on both of them, not just one or the other.