I think you find out more about the pro's ability when they are given someone with potential rather than someone with very little potential.
Vincent did well with Rachel, but although Edwina had some ability to move well, there's only so much Vincent could do.
Flavia did well with Russell at the start, but it quickly became apparent that there wasn't a great variety of character in Russell's dances, which limited what Flavia could do. With Matt D'Angelo she created many great routines for him, which unfortunately his brain lost track of occasionally (maybe due to working on Eastenders too).
With Chris, Ola did choreograph to Chris's limitations and there were only a few steps that Chris could do well. There were no bent knees in his Tango, his hands were much the same at the end as at the start. Ola did a good job and made a lot of the routines entertaining, and in the Charleston Chris found a dance he could really shine at. He struggled to remember routines but with Ola's help he never gave up and they won for all the others things they had plus acceptable dancing. Ola's first year she had Spoony, who was maybe the partner with the most potential but they never got far enough, probably mainly because Spoony had no fanbase and with Ola being new, neither had she.
My point is, a lot of the pro's are very capable but major factors are the celebs popularity, personality, previous dance training and ability to learn to dance.
The very short lead in to the first dance now (which can be 2 weeks instead of the 6 weeks they once had) means the pro has much less chance to teach them dance basics and it becomes a sequence of rushing to learn a new routine each week.