Its literally NOT.
The main selling point of D2 was how SOCIAL it was:
1. 8 player games.
2. The battle.net lobby which was cutting edge in the 1990s. It promoted cross-pollenation between Diablo, Starcraft and Warcraft games and lifted all 3 up.
3. Communication between games while in-game which was cutting edge in the 1990s.
4. Helper builds like enchant games.
There are a billion games out there catering to introverted players. That field is picked clean. There are few if any games catering to extroverted players. D2 set itself apart from others in its field by building a massive support network and game design that cater to extroverts. It cornered a market there. And it thrived. By catering to social play, it held a competitive advantage in its field. it had a value-add.
D3 threw the competitive advantage away.
1. 4 player games
2. The battle.net social community was COMPLETELY destroyed and battle.net was turned into a stupid launcher.
3. They almost didn't include chat channels.
4. Helper builds are gone. Helper games are gone.
D3 is designed more to be played solo. Wonderful but there are a billion games like that. So there is no value add. There's no hook. There's no competitive advantage. So no-one plays D3. They needed to build ON TOP of the social play D2 had and take it further. Instead they went backwards. Instead of taking the lobby idea and adding more features, its gone. There should be a modern lobby where overwatch, Diablo 3, WoW and SC2 are all linked for the purpose of facilitating the ability to jump between games seamlessly to cross-pollenate like the old bnet did. And that's just one example.