I think that the value of a lot of unions is obscured by how well-established they are. Historically, unions are a solution to a specific problem - the employer can (for one reason or another) get away with jerking employees around and treating them badly. But if you form a union, and the employer is forced to stop some of their the worst behaviors, and then it stays that way for a generation or two, it feels like the union serves no purpose.

To take government work as an example: you mentioned some minuses that are very obvious. But you didn't mention what I consider one of the biggest pluses: not having to fear losing your job because the mayor/governor/etc flipped parties. That still happens in leadership positions, but it used to happen to rank-and-file workers as well; I believe it's the public employee unions that stopped that.

I don't work for Amazon and I don't have a dog in this fight, but it would've been very interesting to see what happened if this site had unionized. It's not really clear to me whether/how much Amazon is jerking its workers around; are there plants really unsafe, are people really miserable, should they be paid more? Having one site unionize for a couple of years would probably answer those questions better than a million forum posts.