> I don't know how we can be confident a Union will just solve the problems you point out.
Unions increase worker bargaining power. If worker bargaining power is low, it solves that
> if you are low-skilled or no-skilled, then it does not matter how much value you bring to a company
The amount of skill has nothing to do with it. Only your marginal product of labor and the ratio of your pay to it
> you are too easily replaced
That would affect bargaining power, correct
> The solution isn't to fleece the company, but improve the average person's ability to obtain valuable skills, no?
Not particularly.
For instance, low skilled job are also easily replaceable. Walmart is hiring just as well as Starbucks or Target.
So why is the balance struck at this wage point? The issue is that there are relatively few firms offering a ton of the low skilled jobs. The firms are forming an effective union (oligopsony for the technical) which suppresses wages.
> Union shops are notoriously poorly run, poorly organized and inefficient.
[Citation needed]
Public sector unions (eg. police unions, teachers unions) tend to be terrible, because the government doesn't face profitability pressures like companies do.
Some private sector unions have been inefficient (eg. Detroit auto workers in the 1990s) but that's also often because the sector itself is immune to competition (chicken tax for auto workers).
Other private sector unions for instance are much better at ensuring labor norms are respected.
All in all it's hard to go against David Card's (author in NBER review paper above) opinion on the matter of labor economics