Since when and who use the achievement as a benchmark to measure a player's performance?

Well i've been absent in wow for more than 7months, before that non cares about achievements, and u'll always get a raid spot whenever you want. When

im in dalaran, i see those who looking for mate to raid, i pm and then i raid.

Now everyone was like 25naxx LFM need dps, any class will do, then i was like yay i can join them for naxx since i never been there b4 7months ago and i

decided to give it a go, but then wtfbbq when they ask, got achievement for naxx? no? ok bye bye. WTF

so for those newbie who playing alone and hardly get a raid spot even in guild, does that means they wont be able to raid for the rest of their wow life?