Try to see this through the perspective of vanilla/tbc/wrath raiders. Is mythic Archimonde easy? Hell no, but human nature is always to pick the path of least resistance, as long as there is LFR, normal(flex) the subscription numbers will keep bleeding. No i did not get to kill Kel'thuzad in Naxx 40, not many did. I was probably not good enough at the time either, i've always been pretty casual. My guild cleared up to Naxx, and a handful off bosses in it. We had a so much fun, despite all the farming and grinding it required.
The graph is sarcastic, kinda.