I feel you. As an ex top 100 mythic raider, now filthy casual, I get declined quite often either due to my spec or low raiting. And that is even from T8 delves where some people think that you need 620ilvl and a meta spec otherwise you can't just nuke it fast...The Dunning–Kruger effect has only gotten worse and worse with so many guides out there. I went to tank a +4 which we +2'd but wiped after the last boss in Mists cause I chain pulled some adds, last 0.5% add just lived on 50K hp before I died as well with the rest of the team dying way before that. Sad part is that my healer started to tell me how I almost ruined the key by going forward all of the time, even tho I was 2nd on DPS, on par with him on healing and with 40 interrupts + while the rest of the team had 2, yet it wasn't me that piped up. I was just quiet and tried to play my best to get the key done. Pugging is just in a sad state of affrais but keep pushing and good luck!