So, you are saying that your playing of a beta---especially one you are able to access for free---means you are entitled to dictate which changes the dev's are allowed to make to their game? No, that is not how game development works.
If you bothered to read the changelog, you will see why saves made prior to the update are no longer viable. There have been many notable changes to the game (all of which seem to be improvements), and I am personally looking forward to replaying the entire thing so as to experience those changes. You are, of course, free to remove the game from your playlist. The rest of us will continue to appreciate the efforts of the dev's.