Myles Austin and Patrick Crayton did nothing with anyone but Romo, IIRC. Witten in his prime wasn't much different than Witten now, IMO. And Romo may have had decent OLs at times, but nothing like this one. Nor did he have a RB that opposing defenses concentrated on stopping, at least not nearly to the extent they do Zeke.
Crayton was actually on his way to his best season the year after he left Dallas, but got injured after 9 games. Even then, he still had his best season in several categories. As for Miles Austin, he wasn't doing anything with Romo either at the time he left Dallas. It was injuries that derailed his career. Hamstring after hamstring after hamstring, both in Dallas and after leaving Dallas. That's why Dallas didn't keep him.
Even so, Crayton and Austin being in that place at that time doesn't mean they weren't talented. That's not to say Romo didn't take advantage of the talent, but there was talent. As for Witten and TO, they obviously did things with QBs not named Romo. Witten had almost 1,000 yards in a season 2 years before Romo took an NFL snap
Besides, so far Gallup hasn't done anything with anyone other Dak either. But what does that mean other than he started his career as a Cowboy, so Dak is who he got? Miles Austin started his career in Dallas, and Romo is who he got. As for what Dak's receivers have done in other places, this was Cobb's best season since 2015, and Cooper's star has climbed since leaving Oakland and hooking up with Dallas. They are better here than before here.
I strongly disagree with the comment that Witten in his prime isn't much different than Witten now. If nothing else, there is the simple fact that it's very unlikely any receiver is the same at 37 years old as he was from ages 25-30, plus Witten was already falling off while Romo was still the starter. I'll bet Witten's 4.6 40 is probably about a 4.9 40 now, and he isn't nearly as quick as he was. That's not to say quickness was ever his primary trait, but it was at least enough where, coupled with his work ethic and understanding of the game, he was able to be an elite receiver among TE's. I don't at all think his work ethic and understanding of the game are nearly enough to turn him into an elite receiver at TE today. Today he is a solid role player, but not a premier talent at his position