While I don't condone DDoS attacks, the only reason for D4 to be online-only is monetization IMO: Blizzard wants to sell cosmetics, so people have to see other people wearing them. There is little gameplay benefit from being an MMO-lite.
Forced online is literally the only reason my husband and I didn't buy this game. We can't be the only ones and they're definitely missing out on a good chunk of money
I started playing PoE after getting to somewhat endgame in D4. Got to level 60 something and my buddy and I were like....sooo...whatcha wanna do now? Dungeon I guess? Then we just kinda stopped playing. The rubber banding and random lags were super annoying and resulted in many deaths - we had a great time but needs a lot more cookin in the oven.
PoE on the other hand has been super refreshing and non laggy (the joy of 10 yrs of development I guess) and there's soo much to chew on. In a way it feels like a natural extension of D2 (played D2R for the first time last year).
I quit everything Blizzard after Starcraft 2, that game had so much down time, and although it did have an offline option, you couldn't get new technologies as rewards in the campaign, when servers were down. Making it kind of redundant to have the offline mode IMO.
You can call it a boycott, but a company gone bad, rarely turns back to good again.