I'm getting confused. Who exactly uses KDP (i.e., who does this this new no-more-mobi policy affect)? Is it primarily independent self-published individual authors? Small publishing houses? Or do all books, even from big publishing houses, go through KDP?
And if KDP isn't used by everyone to get Kindle books to Amazon, what is the alternative that is used instead?
(When this discussion began I thought all new Kindle books would be affected, but now I'm thinking I don't understand what KDP is

)
Thank you for any enlightenment.