And last I checked they seem to have given up on supporting Diablo 1, and let GoG deal with it instead ? (Its online MP has security flaws.)
And Blizzard cannot run a game if Blizzard doesn't exist.
But even before that happens, you can already see the wasted potential : D3 (and D4) has no modding whatsoever, compare with D2R (though mods there are still heavily restricted and they have also removed normal MP from it) and especially D2LoD legacy !
I don't see issues with online only tbh.