On the other hand, I view my kindle as an appliance, and I don’t need it to have updated functionality. I think this is true of many electronics: digital cameras, printers, misc USB peripherals, etc. I believe Amazon could easily support the APIs it uses, and keep delivering me books that I’ve paid for or borrowed.
Financially, I suspect the kindle devices have a much longer lifetime than iPhones do, and Amazon is still making $$ off of old kindles.
If there were TLS concerns, a partial disablement (ex: can’t buy books from the device) would be way more acceptable than a complete cutoff. I’ve seen suggestions that it’s a DRM issue, and if that’s the primary motivation, it’s pretty disappointing.