They're slowly closing DRM loopholes and getting rid of old hardware. Older versions of Kindle for PC that allow you to remove DRM won't let you download books published after Jan. 3rd 2023, they won't let you use the download and transfer feature to download Kindle Unlimited books any more either. They've given 1st gen Kindle owners/users new hardware, offered discounts to 2nd Gen owners, etc.
I'm genuinely curious as to why Amazon Kindle DRM seems to be so difficult. Whenever I look at the current state of affairs to try and backup my book collection, I find a lot of howtos on how to do it, all of them broken, with people discussing when such-and-such update broke it etc. And on the other hand, deDRMing and backing up stuff from Amazon Video is trivial with e.g. StreamFab. You'd expect it to be the other way around.
They don't have control of all the devices that support Kindle books either. Right now you can read them in a web browser, Android, iOS, Mac and Windows.
