They where? 9th edition started with a massive point increase on all units. I thought it dies out with 8th edition. I could be wrong.
Slaanesh Daemons was kind of meta for a while.
As people have said with certain exceptions (massed Skitarii) you just get a lot of models which do relatively little, and they proceed to die in droves if anything serious looks at them funny. The aim is to die slowly on the objectives - but in practice the meta is so aggressive that's just statistically very unlikely to happen.
Now if you bring a load of troops against someone running a softer list that can't just delete everything, then you can have a big advantage.