Gear isn't really any less essential, it's just dramatically easier to obtain.
You've got tokens, which eliminated Classic era "watch a newly joined druid/warlock get full tier 2 before you finish your own set, because drop rates are retarded."
TBC added vendor gear too, although it was mostly terrible up until Sunwell (and horrendously expensive. Quite a few people ended up farming Karazhan throughout the entire expansion, since it was the most lucrative source of vendor currency.)
WotLK improved on the currency stuff, and moved tier gear almost entirely onto vendors (with upgrades dropping in raids.
Cata had that for awhile but then moved it back onto the bosses, and currently has offset gear in it's place, although with certain slots simply not dropping at all (amulets, capes) so the loot lists are tighter. Combine that with LFR, and gearing up just happens faster.
You're still not going to get away with doing heroic Dragon Soul naked, but the point of the matter is you're getting set bonuses faster since all three sets (LFR, normal, and heroic) work together, more chances to obtain it, and generally shorter trash than the hours of clearing older raids had.
And to be honest, I don't really miss the Classic era gear checks. The difficulty should be based on the encounter, not how long I've been farming the previous bosses.