MBAs and excessive IP protections. The Warcraft 3 mapping community spawned entire new game genres and franchises. Warcraft 3 Reforged style TOSs means that probably won't happen again.
Blizzard missed the opportunity to capitalize on Defense of the Ancients and as a result they created their own worst nightmares: League of Legends and DotA 2, two successors of the original DotA map.
By the time they released their own version, Heroes of the Storm, it was too late.
Not to mention many other MOBAs that are direct copies of DotA such as Heroes of Newerth and many others.
That, and projects like Diablo 4 were the signs that Blizzard is now dead inside and starting to rot.
No sane person would make those decisions. Those decisions can only happen when a company is ran by powerpoint-oriented people that is disconnected from the customers.
MBAs are the reason China will eat the US.