Assassins didn't exist in order to make everything but damage obsolete - only to counter greedy damage builds and keep adc's in check. In the past if your adc died before 30 minutes it wasn't the end of the world, believe it or not.
Adc's exist solely to make damage the meta. Thus, now that it's the adc meta everything has been stripped away but damage. Yes, there is still CC, but there's so much instant protection that CC is meaningless versus superior numbers. If you can't burst someone during CC there's no point to having CC at all now. Just have enough ranged burst and sustained dps.
Everyone has easy access to Grievous Wounds now as well, via 2 easily-accessed items which is such a slap in the face to anything that ever hoped to withstand sustained damage in a teamfight. Not to mention defensive stats are completely invalid unlike before - you only build them now if there is absolutely nothing else worth building. I'm pretty sure crit items on Cho'Gath wouldn't be terrible at this point.