I mean, you aren't totally wrong. The issue is that I've been playing with the same group of friends off and on for 14 years... and not everyone still has it. Here is our group and our issues...
Me, DK tank 370 ilvl and 27 neck with almost no raiding. I fuck up here and there, but I put in time, research shit, prep, etc. I'm old school wow serious and pull about 7k DPS tanking.
Druid Healer, Ilvl 366 with 21 neck and no raiding. Great fucking player, best on our team, but he's had limited playtime this expansion. Pull between 1-3k DPS while healing.
Shadow Priest, Ilvl 361 with 28 neck and no raiding. Also great player who puts in time, but has had shit luck. Averages 11-12k dps but bitches about shadow constantly.
Outlaw Rogue, ilvl 368 with 24 neck and Raids. Super nice guy, pulls 11-13k dps, but dies constantly. Great attitude, but needs a lot of calling out to not die or to interrupt, etc.
Lastly, the real problem child. Afflic Warlock, ilvl 358 with ? neck, maybe 16 or 17 and no raids. He is pulling 7-8k dps (with me, the tank sometimes outdamaging him), on top of that, he gets hit by every mechanic, and is just really bad. It's crazy because he used to be super great, was a monster, but it seems like the last couple of years he just plays stoned, doesn't keep up with anything, and is just 100% dead weight. We are basically 4 manning most of these, to the point that we are all frustrated and talking about telling him that we're sorry but he's just not going to be able to go. It just sucks, because the 5 of us have been shit for years and years, but it just feels like he is burnt out and doesn't care. I about lost my mind last night when we completed a 10 and I told him to use one of his coins for another shot at loot, because its the highest possible loot he could get, and he goes "Where do I even get those this expansion?" and I just went "Are you serious? You haven't bought any this entire time? Have you been killing world bosses every week, doing arathi,or islands?" and he just sighed and went "Nah, all that shits the worst, I pretty much just log in to do these dungeons with you guys every week."
So yeah, the problem with trying to play with friends for fun >_< sometimes your friends are the terrible pugs.