There seems to be some implicit feeling that everything ought to be getting better and cheaper than it used to be.

It's less an implicit feeling, and more explicitly what's being marketed to us. Think about AI. It's being marketed that it will make everything better and cheaper. Computers before that. Machines before that. All kinds of things in between.

I don't doubt this is possible, especially if these technologies are properly democratized, but greed gets in the way, of course. No one wants to sell you just one fridge at a respectable mark up. These tools don't really go into making a better fridge, per se, but finding what you're willing to and how frequently you're willing to replace it and design planned obsolescence around that. They add subscription features. They want you to log into your fridge to track and sell your behavior, etc.