The problem with electronics in cars isn't so much that it's difficult to repair, as that it's all proprietary vendor-specific secret sauce. Diagnostics are limited and prohibitively expensive - you take it to the dealer and they plug in their test computer that says there's a problem with the foo sensor, so you replace that and then it starts moaning about the bar valve servo, so you replace that and it doesn't fix the problem and then the next logical thing to try is a new ECU but that's more than the car is worth so you scrap it.
Same principle applies to most e-bikes, and indeed Di2. It's just that they're an order of magnitude less complicated than running a modern internal combustion engine, so I expect the mean-time-to-uneconomical-repair to be somewhat better. I expect that batteries dying of old age will be the usual failure mode, with newer better systems looking much more attractive than an expensive replacement battery.
My parents had a B&W telly from prehistoric times (or at least the early 1970s). It fell off a shelf in a caravan once when I was small, failed to work, and gathered dust in the loft for years. As a curious teenager I dug it out, opened it up and discovered two things: Firstly, a broken inlet fuse (looked to be the result of mechanical trauma rather than overload), which on being replaced restored full functionality. Secondly, folded up within a slot on the inside of the chassis, a complete schematic, including part numbers and photos of oscilloscope traces at all the important test points. Anyone with sufficient electronics knowledge could have diagnosed and repaired a fault, or indeed built their own copy.
Modern electronics is the equivalent of glued together plastic parts. The ways that they're commonly engineered to maximise profit margins on consumer products are no more inherent to electronics than they are to plastic.
