Romo was better moving around in the pocket and avoiding sacks. As a matter of fact, he was the best I've ever seen in the pocket in my 30ish years of watching football. His mobility consistently avoided sacks and extended drives. Dak doesn't have that trait. Go back and watch actual game film...or better yet, look at the roster and consider who was blocking for both.
Dak has had Martin and Smith anchoring the line throughout the entirety of his career. His worst full time starter was Connor Williams, and he did well for Miami after he left. Romo was working with guys like Phil Costa, Cory Proctor, Kyle Kosier, old Leonard Davis, Old Floziel Adams, Doug Free at LT, Montrae Holland, Nate Livings, Ryan Cook, Mac Bernardrau, etc etc....not to mention, Dak had an elite blocking back in Zeke every year except for last season.
That line started to come together when the trio of Martin, Smith, and Frederick were in place....the end of Tony's career after his body was cooked. That's what Dak had to work with. Frederick got sick and they brought in Biadasz, who was solid. I'm not saying Dak isn't as good as Tony was, but Tony had something that Dak doesn't that could compensate for lack of talent in the trenches. How do you think it's going to work out when Dak has the same talent along the lines that Tony had?