It is dead. Both player-wise and development-wise. There hasn't been interesting new content in 1-2 years.
That's part of why there was so much hype for d3 at Blizzcon. People were expecting something big, since it felt like they just gave up on d3. And after Blizzcon it looks like they really did.
Even Kripp who's known for getting drawn into games and no-lifeing for weeks at times just got disappointed by the direction the development is going. After that he played d1 (because the d1 event in d3 which is the thing that disappointed him so much) and even that was more fun lmao.