Except the 2nd most popular post on /r/Games is about how Artifact hasn't had any updates in over a year now... So 4 weeks in the middle of the holidays seems a lot more trivial.

That's a quite different situation, Artifact is a dead product while Stadia is a recently launched product.

Try asking the CSGO community whether or not Valve manages to communicate at all. It's a very common refrain in that area about how silent Valve is and the lack of attention the game gets, despite being the most played game on Steam.

Largely CSGO seems like a finished product. Its the result of almost 2 decades of refinements and other than a map change or weapons price adjustment it doesn't need anything done.

At this point it feels cultural and engrained in their DNA. There's no way this can keep happening otherwise.

No doubt, but it was engrained in Valve's culture too, yet they managed to fix it.

How large is Valve?

Around 800. It's not really a relevant factor though, the size of teams shouldn't impact the quality of their communication work.

It's relevant towards how much institutional momentum there is to overcome if you want you team to do something Different From Usual.