Below is an interview between former World of Warcraft devs. Kevin Jordan, like Mark Kern, is a Vanilla-era dev that stuck it out longer than that. Chris Kalenki just left in the last few weeks. The interview concerns Blizzard, WOW, and the corporate culture change over time into its current degenerate state. It's movie-length, so feel free to watch it in chunks if you don't want or have the time to spend in one go.
The TLDR is that the post-Activision climate in the office increasingly reflected the Activision culture and squeezed out the Blizzard culture. There was no need for a formal mandate to come down from on high; changes in personnel to put people already embracing Activision's perspective was sufficient to make this happen. (Outsiders and turncoats taking over something someone else built and warping to serve their ends. Sounds familiar, oh you what deal with SJW covergence?)
Most of the changes reflect Standard Corporate Management Protocols with all of the stupidity that entails. Retroblasting's video on it remains as fresh as the day it went live.
This is why there is no fixing Blizzard in the way so many players think can be done. The only thing that can be done is to close your wallet and walk away, especially with the increasingly obvious neglect on enforcing things like mass botting by gold farmers that lag out servers and wreck in-game economies. Don't buy Diablo 4, yadda yadda yadda.