No one wants to spend 3 hours in a dungeon with a bunch of strangers that can't play for shit.
When I first hit level 70 back in TBC, I spend something like 5 hours in Shadow Labyrinths. 5 hours. With a bunch of guildmates. We were on TeamSpeak, we were having a laugh. We were failing miserably, but each pull we got a little more down. We never did get to kill Murmur that night, but it was fun.
My patience with random people who all want to blame everyone other than themselves for wipes, is rather less. I think I once spent all of 10 minutes trying to convince people to move away from the charge on that first boss in Grim Batol (without yelling at the healer for not stopping you getting one-shot). If all you get for trying to explain tactics is "FFS HEALS", then you're going to get out of there.
There are varying levels of skill and varying content to match. I lament the loss of hard heroics as much as anyone, but they just don't work in a post-LFD world. This is why you can't group for Challenge Modes. I'm not convinced that blasting through as fast as you can in enormous terrifying pulls was a step in the right direction, but it was at least a step. An admission that people's ideas of what heroics are, differs from player to player. One size does not fit all.
It would be nice to have a heroic be hard, and not randomly grouped for. Something that it's expected that raiders will do, but not be the base step before going to LFR. Where the queue just puts you in a level 90 version of a dungeon, while having a full group of 5 opens up the real heroic mode.