There is a company called Jagex Ltd that made a game called RuneScape that was a juggernaut MMORPG and still exists. What I can tell you is that after Andrew Gower, the majority share holder, sold his shares and retired as CEO of the company the game slowly implemented more MTX over time. You cannot log into the game now without having offers to buy spins.
The leadership Blizzard has lost may not necessarily be significant in the day to day development done by developers but where they will be missed is as voices that hold back the tide of microtransactions that are currently plaguing the video game industry.
Blizzards first game that was heavily MTX based in a negative way was hearthstone. You had a lighter fare of MTX with Heroes of the Storm and WOW cosmetics. You have Diablo Immortals on the horizon.
What you need to watch is who controls the decisions over MTX implementation because games with over burdensome MTX blows ass for gameplay. We will see where this goes.