I agree to an extent with what you've said. I think labor is a balance. GM had it swing too far toward labor. However, if you're an auto worker, there's likely only one employer in your town which gives that employer undue power. Ideally, there are many employers that demand the same skill set that you can get a job with. In that case, you have the choice of many firms and the firms have the choice of many workers and it works out pretty well.

Since there are only a few auto manufacturers and the likelihood that there's more than two in your commutable distance is low means that auto manufacturers have the power necessary to abuse their workers without unions.

However, unions became ultra-effective in many places demanding things like pay even when plants aren't used and benefits fit for a king. GM agreed to that because, at the time, the auto industry was really just Ford and GM and the unions were sticking it to Ford too and so it didn't matter so much. That's changed, but the UAW won't face the post-80s reality.

Having workers have no power is bad. Having companies have no power is bad. Having each group have equal power works pretty well.