You're free to ask.
But remember : you're asking a paid performer to evaluate the performance you paid them to participate in
If they say you're incredible, is it because you are, or because happy customers return ?
If they say you need work, is it genuine advice, or a reason to keep coming back ?
So the problem isn't getting feedback. The problem is knowing whether the feedback is honest, strategic, or simply part of the service.
Because business transactions are terrible places to look for unbiased validation. In industries built on persuasion, the line between honesty and flattery can get blurry. Not everyone is a liar, of course, but some professions reward persuasion more than honesty.