I never bought into Kindle because of this lockdown attitude. I buy audiobooks from audiobookstore and ebooks from google play books when lazy and itch and the other usual independent sites that sell drm free files when I'm not doing a jit in time purchase. I have a kindle I USB sideload or put files on sd card, because it has a physical keyboard.
But with the state of digital goods disrepect for the customer and locking us in mustache twirling reasons, I have better ways to spend my income. Yes I am not above reading shadow copies of books at times, but I'd rather kindle sell all titles as DRM free on rootable devices and their convenient storefront would be enough for me to direct my business there more.
The Kindle isn't a bad device on its own. Personally I use a Kobo. But I never pay for any ebook that I can't keep indefinitely one way or another.
I also have an old Kindle 4 that needs to be jailbroken before the May 30th deadline. Maybe I'll do that today. Gets you out of the ecosystem. And old Kindles can be found pretty cheap.
I used to feel this way, but I reconsidered my threat model. You know what format is "locked in"? Physical books. Can only exist in one location at a time. If you loan it out, you can't read it until it's returned. Subject to theft, fire, rot, bugs or simply being lost.
There are aspects of Kindle I don't love--the constantly changing cover art for books I've purchased--but I've never run into an actual problem. I've got 2,500 books on my Kindle devices, and I can access them anywhere in the world at any time on my dedicated readers, my phone, my laptop (via Kindle Cloud Reader).
If DRM is the price I have to pay for a dead-simple ecosystem, multi-device support and free cloud storage, well, I guess I'm happy to pay it.