The sad part is that it kind of does work from the other end.
Suppose you're a former press operator who can't expect to find any more work operating a printing press. Should you take a McJob? You have years of experience working with electric motors and hydraulics and pumps and industrial control systems. You might be better off to get a job in a trade. Study for the licensing exam and become a plumber or an electrician or the like. Except that you can't, because you're required to do a multi-year apprenticeship to get into any of those things no matter how much experience you have doing something similar. And you can't even get the apprenticeship to begin with because you're 45 years old and the union won't take you.
When a job is being eliminated by newer technology, the union has essentially no power because the employer doesn't care about workers going on strike when they're about to be laid off regardless. But when those laid off workers then want to get a job in another industry, the union there shows up to exclude them.
Which obviously sucks because then the union is screwing the laid off workers rather than some faceless corporation we might imagine or prefer them to be screwing.