I can't think of a single release from them I would describe as 'ambitious' other than Diablo Mobile which has the distinct honor of being dead before arrival.
Speaking anecdotally, no one I game with or any of the forums I go to talk about Blizzard games. Many of the Discord servers I play with used to be big into HotS and Starcraft I/II, but I don't hear a peep from them about either anymore.
Perhaps worst of all, several of the Path of Exile players I game with are no longer even worried about a Diablo 4 launch affecting the long term health of their favorite dungeon crawler. It's just expected that Blizzard will deliver a polished but shallow experience that will be over within two or three months at most.
Maybe they just aren't nimble enough anymore to leverage their huge war-chest of experience and cash.