professional-incompetence

Someone who is bad at what they do, someone who really doesn't know what they're talking about, but they do it in a way that seems outwardly proffessional.

Adjective form: proffessionally-incompetent

It Doug has so much professional-incompetence, he posts his own drivers-ed tutorials online, but he doesn't even know how to drive.

Sarah is professionally-incompetent, because she really does look like she knows what she is talking about, but the pros mock her, because to an outsider she looks like she can talk the talk AND walk the walk, but her catwalk is not a real catwalk; she would hurt herself on a real catwalk.