Factory workers weren't (and even today really aren't) a replacement-level job that anyone can just go out and get. A guy making $4.50/hr at GM in 1970 had a great job that his peers would have envied; quite a lot of people who worked just as hard were making $3 or $2.

Sure, but the 2025 equivalent of that GM job -- if you can find it -- is not going to pay enough to support a family and pay a mortgage on one income.