Carla is a decent wrestler for WMMA, problem is actual good wrestlers on the women's side are about as rare as high level strikers so she's more decent by default than anything else. An actual high level wrestler would not be struggling with the likes of Markos or Calvillo, and it's in the latter fight where you can see the problems with Carla's wrestling (you can see it in the Joanna fight as well, but that's kinda not fair).
Esparza doesn't shoot from a good stance, she leans forward and ends up trying to drive a shot from her knees. Instead of level changing and shooting from a stance that's similar to a football lineman's and getting a powerful drive from the legs & hips, Esparza either a)essentially falls forward until her knees are almost on the mat before trying to drive off or b)leans way over at the waist and tries to drive forward without getting her legs & hips under her. This means she can't get power & penetration on her shot which was why Calvillo and Joanna were able to stuff it so easily. Contrast that with Claudia who does level change properly and shoots from a strong wrestler's stance, even when opponents try to stuff the shot there's so much drive behind it that they still get blasted off their feet.