gibustransparency is never bad unless youve got something to hide
I would disagree very much with that. When a developer states something or promises an update or whatever, you are resigning yourself to fulfil that promise. While that seems like a good thing, it becomes extremely limiting and for a company as volatile as Valve, change is a constant. By becoming more transparent, you risk a larger amount of your player base will become hostile to the changes put forward.
People freaked over "Neato" for Christ's sake, let alone a insight into the developers' mentality and goals. If Valve came out with "We're working on a MvM update", the competitive scene would believe that they have completely abandoned competitive. If competitive is the focus, casual players will claim that the focus is killing off what made the game popular. By not speaking at all, they ideally could listen to what people are saying or reading feedback from emails, etc and work on delivering that through updates and such, which has been the method of communication from Valve for the entirety of the games history.
Nowadays though, the TF team don't have the manpower to sustain that method and because of that, the game feels abandoned and crucial fixes seem like they haven't been patched in years (Det Bug). You can't blame Valve for focusing on more lucrative or innovative ideas, especially due to their transition from Games to Hardware/Software.
Transparency only works when there are enough people there...and even then can do more harm than good. See: Overwatch.