The game took a dive when he left and it was primarily because of system design issues. Ghostcrawler was apart of one of the best expansions in terms of system design(MoP). Optional challenge modes with rankings and cosmetics. PvP power which meant gear for PvP came from PvP. Fully optional pet battles. Valor, Conquest, Reforging, Thunderforging. He understood how to make content last without forcing players to do it or giving massive rng incentives like titanforging and Legion legendaries. The worst parts of MoP were the beginning daily grinds and maybe the legendary cloak. Those 2 things pale in comparison to the atrocious system design from Legion, BFA, and now Shadowlands.
Bit concerned he is playing WoW and has announced Riot are making an MMORPG, like seriously, everyone has tried to copy WoW over the years and failed, forget modern WoW and embrace the good things about old MMORPG's of early 2000's and go another way.