BG3 is a completely different game, one you need to pour your heart and soul, and most importantly mind, into. I don't have the mental capacity to play a full RPG after a full day of work and then playing with my kids and then chores. I have an hour maybe to chill out and BG3 would only stress me because I would forget the story between my gaming sessions and couldn't keep up.
Whereas with a Diablo game I can log in for half an hour and have fun. I can be rewarded finding some loot, or making some progres in my build. It's scratches a completely different itch than BG3.
Sure, that's why I'm not going to play D4 either after the patch, I'll just find a roguelike I like or will spend that time going through my PSVR backlog. But recommending BG3 over D4 is apples to potatoes for some of us.
And with an hour every other day I was not able to keep up with D:OS. It was just too overwhelming with huge story arcs, many characters and everything. I don't have the capacity for that after a long day, it's simply not fun for me.