Are you being outrageous and arguing in bad faith on purpose?
I genuinely can’t tell, in the event that you’re not, nobody has ever suggested that janitors should be allowed to do the duties of brain surgeons. Furthermore, even if a single absolutely insane janitor decided he should be allowed to do the duties of a brain surgeon… nobody else would agree with them, because we live in a society with vaguely reasonable humans… and that janitor would likely be democratically FIRED for suggesting something so outrageous, or put in a mental institution.
Or are you worried about the janitor uprising in which janitors decide they can do all jobs known to man? Perhaps nothing can stop the janitor uprising, and we are all doomed.