Remember when skill mattered more than gear? I do, at least for PvE. Oh these weren't some sort of mythical glorious times when we were all incredibly skilled and needed no crutches. We weren't amazing back then, contrary to the myths some people like to spread. Most raid fights were pretty simple up until AQ.
But we raided in blues. We did instances in blues. Or no, that was when we were overgeared. We did Scholomance in greens. This was like running H UP in greens because back then Scholo was badass. 'Heroic' mode was going in with only 5 people since the quests couldn't all be done in raids. That was half-strength.
Again, I'm not saying we were awesome. You could do H UP in greens now. But why would you? You don't have to. We did. Back then gear was harder to get. No badges, no easily overgeared entry raid to farm, no heroics dropping epics at the end, crafted items were incredibly expensive and often not very good. So we wore a lot of greens, blues if we were awesome.
After a while MC was being farmed regularly, but if you had MC gear you weren't going back to the 5-mans. With no badges there was very little incentive. Rep? You got that when you were running the places a million times for your dungeon set.
To further increase the weakness of gear, it sucked. The gear was horribly designed. Spirit all over the place, no mana/5, no int->regen talents. We stacked int (as much as one could before gems and a wide selection of gear) as casters because we sure as hell weren't going to be regenerating mana, so we'd better have a lot. Hybrids were in a particularly bad spot. Shamans struggled to find strength mail (back then it was our main stat, because we could effectively share hunter gear) and when finally hunter agility was nerfed and they added AP to gear, it was a glorious day. Spell power didn't exist and shaman mail meant healing mail, not elemental. Druids weren't any better off, though at least they could get rogue gear. Paladins could get warrior gear, except then they had no mana and had no regen back then either.
So we wore our greens and proudly proclaimed that skill > gear, not because we were amazing, but because our gear was just that bad.