I wouldn't claim "cannot ever" (and after all, to some extent repairs are worth it even under today's conditions), but I do believe repairwork is simply inheren

I wouldn't claim "cannot ever" (and after all, to some extent repairs are worth it even under today's conditions), but I do believe repairwork is simply inherently more complex and difficult to automate. Unlike in assembly, there's not just one happy assembly path that you need to handle – first you always need to diagnose the problem, and then depending on the problem take a variety of actions in order to fix/replace whatever you've identified as the faulty component. Plus subsequently, even in the ideal case of a widget that's as easy to disassemble/repair as it was to originally assemble (which comes with its own set of trade-offs), any productivity gains in manufacturing that were based on parallelisation are difficult replicate when repairing just a single one-off component. E.g. reflow soldering allows you to efficiently solder large circuit boards with hundreds or more components in one go, but conversely subsequently replacing just a single one of those components therefore doesn't take one hundredth of the original assembly time.