In south korea, where unions have strong political power, they have become a social problem. Union members of corporations like Hyundai are notorious for demanding guaranteed job entry for the children of the workers, protection from termination due to sexual misconduct, etc. Strong unions are not always good in that they form a faction within the corporation and become very toxic.

Also I don't think it's fair to compare the 1950-80s to now. The 1950s-80s was when America had little to no competition in global economy and was the centre of global manufacturing like China is today. So it would not be fair to assume what worked then would work now.