“Progressive” is a code word for Communist.
All the leftist labels are codewords for communism, or at least collectivism (that ultimately has to lead to totalitarian communism).
They keep changing the label because people figure out what’s in the can, and the word on the label comes to mean the crap that’s in the can.
This is the same with any group that keeps changing what they “prefer to be called” - the new moniker comes to mean the same thing that the previous “derogatory term” meant.