Unless they have a Judo/Sombo or Greco background, most fighter’s upper-body takedowns are garbage. Hendo, Shonie Carter, Couture, Lindland (all Greco guys) and Parysian, Yoshida, Nakamura and Fedor (Judo) are the only skilled throwing technicians I can think of. The rest of the guys are ex-high school wrestlers or have basic wrestling/takedown skills (obv in comparison to the best fighters) at best. They know the double and thats about it.
Some of them (especially BJJ fighters) can’t even shoot a solid double (see Royce, Nogueira et al). Most of them just pull guard or muscle their opponent down (see Arona). Their ‘Judo’ or ‘wrestling’ skills are sub-par compared to a new-to-MMA Kaz Nakamura (back when he fought Little Nogueira for the first time).
Sure Nak was a National level Judo-ka, but you have to learn to adapt your Judo to no-gi obv and even a new Nak did that most impressively. The only BJJ guy I can think of who was impressive with his throws/upper-body stuff was Ricardo Almeida v. Lindland where Almeida even took a silver medalist in Lindland down.
I’m not sure why, but why does no one try to throw Liddel or Cro Cop, for example ? The obvious answer is most people don’t have the skill to do it. Why they don’t attempt to add to their repitoire, I have no idea.