Cataclysm-era destro certainly had sh*tloads of buttons to press, but every single one of them was very weak. Lots of effort without feeling rewarding at all. Complexity is fine as long as you get some reward from it. But that was not the case here-- due to the general weakness of all those different spells, Cata destro had no way to shine in any fight, except perhaps Morchok/Korchom -- which was a meaningless easy intro fight. Cata demonology, in contrast, was at least slightly rewarding in its complexity; if you got the prepull gearswap Moonwell Chalice pre-soulburn petswap opening shenanigans with its 20+ different action buttons just right you were rewarded with an awesome dps for the first couple of minutes, which was great for farm-status heroic Ultraxion, for example.