Kindles can only (easily) do what Amazon wants it to do —full stop.
It’s like the iPhone before the App Store.
I bet Amazon would make a massive amount of money if they opened up their ecosystem to let others develop on top of it
If I were head of that division at Amazon, I'd remove bluetooth, APIify the bookstore (so you can buy books from other retailers), remove GoodReads integration, and direct the hardware people to focus on battery life and the software people to focus on layout and typography. I'd also add a physical switch to enable/disable the touchscreen. All Kindles would have physical page turn buttons like the Oasis does.
Kobo's Pocket integration is nice, so I can read through articles I've saved on my computer/phone without distraction. There's also an Overdrive store so I can browser and borrow books from my local library without jumping through hoops.
Would it be nice to support alternatives to Overdrive and Pocket? Sure, but once you open the doors to any third-party apps, it's hard to keep the focus on books.
I use my regular e-ink kindle 100% offline, I never turn off airplane mode. I only load content via USB using the Calibre CLI. I don't want my Kindle to do cool stuff. I used to think I did, I rooted my early Kindles and tried to do as much on them as possible. But then I realized that it's only a distraction from the one thing the Kindle is actually good at: reading long static text documents.