If you don’t understand the problem, that’s on you.
It’s been 6+ years since Diablo III, that launched poorly and many still prefer Diablo II (which was in 2000. See how long of a wait this fanbase keeps having to do?), and the rumors/hype was that Diablo IV was going to be the sendoff announcement for the biggest part of Blizzcon.
Instead, they announce a third-party developed, copycat Diablo mobile title that you can’t play on PC or without an internet connect. When asked about releasing on PC, they said no plans for that, then took a shot at everyone booing saying “Don’t you guys have phones?!” like it was a funny comeback.
Blizzard messed up 100%, and they deserved all the backlash they got/still are getting.