I think people are getting very confused by all this - I certainly was, so I have gone off and checked it. It is not the case that you will be unable to download books on to your computer/tablet/phone - you will still be able to do that and to read them through the Kindle app. Basically, you can download via wi-fi to the Kindle or the app as most people already do.
The thing that is being removed is the ability to download via USB cable. This type of download changes the format of the book that is downloaded, and the "problem" with this is that beyond backing up your books somewhere that isn't Amazon, then the books can be made readable by other e-readers or remove the DRM that prevents people pirating the ebooks.
Now you can have your own opinion about whether this is "fair" or not. But for probably 99% of people they buy Amazon e-books because they have the Kindle or the Kindle app and it will make almost no difference to them at all. The point about books being removed from Amazon "permissions" may be an issue for some people, as might automatic updates if a book changes in some way, but probably very few (and most of them probably didn't know about the possibility either).
So for most people the change has no impact at all and they won't notice anything different. You are not tied to Amazon devices - you are tied to Amazon software, and many of us thought that was the case anyway! Or couldn't be arsed converting the books to other ereaders when you have a Kindle and / or at least two versions of the app....