These aren’t related matters/motivations or even related posters. Most people whining about 1. are ill-informed and ho-hum about the speed and power of top 100 parses when placed next to their very odd memories of how Vanilla ought to be. The people talking about 2. are the usual min/max crowd who correctly advocate for bringing ideal gear, specs, classes, buffs/debuffs, boss kill strategies, etc.
The game is easy, not because of 1.12, but because Vanilla was simply easy. The most complex raid encounters in AQ40 and Naxx just don’t hold a candle to some of the 5man mechanics of later expansions in terms of individual skill and responsibility. Couple that with very simple rotations and the game is just not hard and never was. However, there is enough freedom for every player to make their otherwise top-tier DPS class into a pile of steaming crap that an AFK-autoattacking Resto Druid in Cat Form would beat on the meters. That’s why the Vanilla content is so forgiving, it compensates for the absolutely abysmal, barely above 0 DPS, levels of silliness that can be accomplished by the player base. It just so happens we can all easily put our raids in the upper 20% without much effort now and we have the tools, experience, and models to support it.
But knowing that the game has a lot of slush baked into it all means that if you have a raid full of weirdly spec’d and geared DPS, you will take forever to kill things, you will fail at otherwise easy mechanics, you will run OOM, you will have Tanks die, etc. I’ve seen Druids running around in absolute tip-top DPS gear doing exceptionally well in raids, giving Rogues and Hunters a run for their money on some fights. I’ve also seen Druids that insist on playing like a pure-hybrid with a mix of all talents and all stats and try to do DPS only to get beat by the Tanks, and by a large margin. Vanilla oddly taught people to maximize all of their tool kit or they were bad for Reasons™, so you got Mages weaving in Arcane Missiles between Frostbolts and attempting to maintain various Wards, just in case, you had Druids tossing out anemic heals before jumping back into Cat to put up bleeds, and you have World First Rag kills where the Rogue isn’t even using Slice and Dice but boy-howdy is he spamming Feint off CD.
There are lots of opportunities to play this game very very badly just from the talent and gearing foundation, all the way up to all the silliness of bad rotations and odd/pointless spell usage.
You can still wipe to Lucifron if you have a raid full of morons playing however they want to play, you just don’t have to, which is the point of teaching min/max.