Contriving a straw man to argue a position does no good.
I specifically took issue with claims that it's thoughtless. That in no way says it's right or wrong [1], but I'm extraordinarily certain that a lot of people thought long about every detail of this, they probably argued and different people had different takes, and we can see the results of that process. Trying to casually dismiss all of that as thoughtless is gross.
> Aren't unhappy users valid enough data to demonstrate a downgrade in user experience?
Unhappy users aren't proof of much at all but that people really dislike change, and that you can't please all of the people all of the time. The eventual net result is an entirely different thing.
And again, the net might be positive and it might be negative. I've made zero assessment of that. I happen to be a pretty malleable user and I just flow with whatever, adapting to whatever various platforms demand I use.
[1] Although notions of right and wrong depend upon the inputs to your assessment. e.g. often we'll some users feel that a certain function or trait is a first class, primary element, while it isn't to others. What is right for one can be wrong for another. Seldom is it universal. Every design of any complexity is wrong for some subset of users.