My uncle has a basic HS education and no real marketable skills. He's a custodian who belongs to a Union. For him, and people like him, I can see why they join.
I also worked for a company where the hourly people were all unionized. I don't know all of the details (wasn't a member) but my understanding was that they had no real negotiating power with the company - they were "collectivized" more for benefits than anything else. In general, the arrangement worked to both the company's favor AND the union's.
So - there are places where unions make some sense, or at least I can see why people belong to them.
In general, though, they're useless remnants of a system designed to resolve issues that disappeared decades ago.
Traditional management can’t coordinate something like that?
Count me skeptical. Such management might include cleaning ladies (and gentlemen) who made it good. They wouldn’t have to be ignoramuses.
Or maybe you are talking about something like a contract house?
A real union wouldn’t allow much, if any, competition.