Rescorla forgot that MOP's talent revamp left a lot of classes with gobs of shit that took up more hotkeys than could be bound on any keyboard a human was capable of operating with one hand and that's why abilities were pruned in WOD. That and every class in PVP felt like it had 150 points worth of talents with all the CC and utility cooldowns because so many prior talent choices were baked into the classes across all specs. And on top of that, they added a bunch of new abilities to flesh out all of the new talent tiers - many of which were nothing more than an extra button to push for 2% more damage. People didn't like it, Blizzard didn't like it, they addressed it. Was it perfect for every class/spec? Certainly not. But it seems to have worked out fine for most. They cut the bloat back to Cata levels, not fucking vanilla. Most shit is still more involved than it was in BC or even LK.
I see that you now want to change your argument to something along the lines of "oh, I mean there should only be one difficulty level instead of all of these options. Because once I do it on the easiest possible mode I feel like nothing else counts." That's a popular argument. But almost nobody else is making these games that way any more. If they do, they wind up with a goddamn civil war on their hands between the shitbucket hardcore and the functionally retarded button mashers and everyone in between.
Look at Vanilla/Burning Crusade, before there was LFR and hard modes. Hard as fuck, then nerfed. Broken as fuck, then nerfed. Hard as fuck again... and then nerfed again. Wipe 500 times to M'uru, kill him two fucking weeks before he gets nerfed into a joke. Was that honestly any better than just giving us a difficulty switch?
Hell, I've never done Hellfire on LFR or normal. There was no incentive, other than practice or finishing my legendary faster. (as a result I still don't have a ring. oops.) But it was rewarding because my first kill on Archimonde and everything else was when we killed them on heroic. That's the difficulty setting I chose. Mythic is just something to do when the loot runs dry, I couldn't care less how far we get. If we dead end, we dead end. I'm far from hardcore, but I sure as hell know better than to run LFR one time and then dash here to declare that the game is "so dumbed down" out of total ignorance and then have to backpedal like a madman.