Fact is that Dak cratered in the second half of the season when Elliott was gone. It doesn't prove that Dak cannot carry the offense by himself (like Romo used to do). But it is a fact that he didn't carry the team this year under adverse circumstances.
Now, are there mitigating factors? Of course. Just like there were mitigating factors in Romo's case.
If I had to pick between Dak last year, and a younger Romo, I would have picked the younger Romo. If you could trust Romo to stay healthy, it would have been an easy choice. But the reality is that Romo was knocked out for most of two consecutive seasons. His body was no longer able to handle the game. The Cowboys were fortunate to land Dak, and he did have the best rookie quarterback season in the 97 year history of the NFL (now 98 seasons.) That's not nothing, and gives all of us hope that Dak will learn from his dismal 2nd half of 2017 and get better. Even Jerry Jones has said he believes Dak will ultimately be better because of the struggles he had this year. But Jerry needs to believe that, because the Cowboys are all in on Dak.
I hope it's true, too. And I hope that Dak (who didn't get the luxury of learning on the bench for over 3 seasons like Romo did) will ultimately be better than Romo. But that jury is still out, and the verdict is a long time away from coming in.
On the other hand, the verdict for Romo is in. His body gave out. End of story, and end of career. He landed a pretty good gig to replace football though.