There was no real turning point in when the game died, it was in a slow decline with every rework
D3 RMAH Vanilla: too random, extremely hard GG eq
Patch 2.0.1: Torment introduction had bad difficulty scaling (still not fixed today but reflected in the difficulties under T1)
D3:ROS
Patch 2.0.6: removal of the GRIND for materials was the worst and especially with the low quest and item drop rates :thumbs-up:
Patch 2.1.0: GRs and Legendary gems
Patch 2.3: CUBE, T7-T10
Patch 2.6.0: Necro meta GR group
Anything after is basically what it is today with tweaks
The game has been moving to a more simplified form of grind which for casual players is fantastic but this ostracized any real D2 fan. Even D2 has carbon copy builds, but there is a sense of uniqueness with gear, which is not reflected in D3 (primals and ancients). D3 tried to answer this with unique leaderboards for X set/X Gear which was a smart move.
It took D3 (2012) 10 years to finally have something acceptable but unfortunately, this won't bring anyone back and even if there is a breath of hope, the
gameplay is far too casual.
Source: playing since beta