I have been playing puzzles more sporadically lately, when I checked my rating I'd lost over 600 back in October, super weird.
They always told you that is for you.. and it's better. They need defend this. But the truth is, that you didn't know, because nobody take care about the users before change the method. Nobody even imagine that maybe good idea is inform the users before. That's the only problem. Months passes, but every day someone ask what's happened? No matter how they try to defend this.. it's no make sense, because they don't think about users and they not admit that was a something to improve. They have so many months to change this. So easy to send message for the users, but big company take money and don't care about users. That's the only reason why you need to be surprised
They announced it in various places on and off Chess.com several months before the re-rating took place.
This was posted by Support in July:

Another was the State of Chess broadcast in September 7th: (at about the 52 minute mark):
I think it you listen to the presentation by Michael Greene, you will understand why the changes needed to be made and how they make sense going forward.
He explained how the rating changes in the last several months before the re-rating were really distorted and how some people ran up their ratings to take advantage of the situation. (For example by playing only easy puzzles and getting a minimum of 5 points on each.) But now everyone is on the same page and I am sorry if you feel like the runup of your rating in the last several months represented something good.
Most people seem to have adjusted to it at this point.
bro 600, I went from 3400 to 1600