the.com/incompetence
The confident execution of a task you were never qualified to attempt.
means A lack of the skill, ability, or knowledge needed to do something properly.
from From Latin competere, to be suitable or fit together; slap on the negative in- and you get unfit, ill-matched to the job.
Peter PrinciplePeople rise until they reach roles they can't handle.
Dunning-KrugerThe least skilled often feel the most certain.
Legal senseAlso means a court or witness lacking proper authority.