Nameless Voice on 3/12/2015 at 01:46
Mostly that the story is cringe-inducingly awful, compounding terrible writing and retconning most of the first Starcraft and Brood War's lore. Add advisers who constantly treat you like a moron and blather immersion-breaking nonsense (my personal anti-favourite is "My queen, the hybrid is attacking you psionically!" - which combines a really annoying voice, telling someone something that they should know and the adviser shouldn't, and being repeated over and over through the level.)
The new units in multiplayer are poorly-thought-out gimmicks, either unimaginative (Tempest) or just completely comical and not fitting with the setting (Viper).
The new Blizzard method of balancing is still there and more prevalent than ever, where they balance by adding or removing random numbers and modifiers to units (e.g. bonus damage to organic flying units) rather than trying to properly balance with systems alone as SC1 did.
Oh, and I think it says something that the Spawn Larvae mechanic, the cornerstone of Zerg economy in SC2, doesn't even appear in the singleplayer campaign - presumably because no one wanted to have to select a unit and issue a command once every 40 seconds per hatchery - despite the fact that it's an essential mindless action all Zerg players must perform constantly in any multiplayer game.
To be fair, I actually almost enjoyed HotS because it was so bad. It was a journey to see what incredulously awful thing they would come up with next, and they generally didn't disappoint.
I think the only level which was actually good was the second one, and that was an installation map not a full RTS map. The one where Kerrigan was just a Ghost again, before the whole re-infestation nonsense.
It certainly put me off buying LotV, though, despite Protoss always having been my favourite race.
