Things clicked big time for Romo around 2013. I think he even said so himself.
I can't find the source, but I'm going to repeat this story anyway. Around that time, he told Jason Garrett that "3rd down is my down", and just started calling his own plays there. Totally ignored the clapping carrot.
Anyway, Romo was a legit MVP, Super Bowl caliber quarterback by the end of his career. He was playing like the best Cowboys quarterback since Aikman, and maybe even better. He just physically could not stay on the field.
Dak hasn't been bad, but he has never shown the same level of high-end ability as Romo. If you paired Dak's early career, LB-esque athleticism with his current mental mastery of the game, then you might have something special. But he really only perfected his technique and command of the offense at the time that injuries started physically sapping him.
Peak Romo was straight-up smarter than his own offensive staff, and also still had all of his Favre-ian improvisational ability. He was going places. I'd compare him to Joe Burrow today - very similar styles and ability. Dak started off like a Donovan McNabb - sort of a thick, strong, inaccurate gamer - and aged or developed into a Kirk Cousins type maxed-out technician.