The difficult of dismantling some of these things to fix things is a significant issue though - you have to have the time and interest in a lot of cases, and at the end of the investment might still have a non-functional item.

i.e. if I spend 3 days figuring out my washing machine, I'm trading leisure time (bought at whatever my salary rate is) for the cost of the machine. If the machine is a nightmare to open up and close, then I don't really blame people for just buying a new one.

A bunch of this can obviously be mitigated: right-to-repair is a good start, but we also need incentives for serviceability - the example you give of being able to actually get diagnostic data is one area (IMO: that should just be legally mandated as open-source, make it a national security policy - which it is IMO). Firmware blobs for chips should also be public - i.e. I've got a few things where the microcontroller is dead, I can source a replacement, but there's no way to get a copy of the onboard programming.

And then obviously, if we could somehow encourage design which means components are easy to remove, that would be great (i.e. logic and control boards should always be mounted accessibly).

I mean, I get it. I'm a nerd that enjoys tackling problems. But the normal response I've seen from appliance techs have been the same. They seem more interested in the commission of selling a new unit than actually trying to fix the current one. In the end my unit probably could have been solved for less than an hour of his time to just jiggle the connection of the hall effect sensor on the board, but he couldn't even be bothered to figure out it was the sensors that were the problem or actually try and make the repair.

I've had similar experiences with other appliances over the years. It's not just a GE thing.