I'm a happy user, I consider that a success in my book.
The point is that less and less people use Firefox, so there seems to be a problem with success in that area, even if you are someone who still uses it (as am I).
I am also a happy Firefox user, but that doesn't preclude me from seeing that Mozilla is a failing steward of Firefox.
As a happy Firefox user, I want Firefox to make me happy tomorrow as well, not just today.
and what about their book?
inability to put yourself into someone else's shoes, is a very big flag. A red one in my book.