I think it can be hard to predict these things. At least it’s not hard for me to imagine someone coming up with a way to make plumbing standard and easily replaceable in most buildings. Sort of how brick walls became something to come off an assembly line a few decades ago. Today we’re back to more traditional bricklaying here in Denmark because the assembly line stuff wasn’t aesthetic enough to keep selling, but the way we construct buildings has for the most part become like building with legos, and a heap of important trade skills that requires skilled tradespeople died along the way. All it takes for things like electricity and plumbing to go that way is for a company to figure out how to mass produce systems that are as easy to plug in as the rest (which has sort of already happened with ikea houses) and take it to world wide adoption.

This is not to say that I disagree with you, but being adaptable is more important than being just skilled. A lot of those typists eventually became secretaries and then spread further out to different parts of organisations, and a lot of them are still there. It’s only the people who don’t adapt who get left behind, and I’d like to point out here that I’m not a fan of that term. As I am Scandinavian that is probably of little surprise to people, but I think society has a responsibility to keep people useful so long that we require them to work until they are 73+.