I lost track of the number of posts during Beta that 'Demo spends too much time mindlessly spamming Shadow Bolt'. Corruption serves the purpose you state; baseline Fury generation, and something to manage between stances. It was never 'just another button'.
I disagree with this too. Destruction gets really involved when a second or third target shows up, it really doesn't need anything else to watch as Havoc shows more than any kind of proc can, the measure of a good player.But Destruction could really use a Soul Fire swap mechanic like Demonology to have something to respond to besides trinkets. Affliction responds to Nightfall, Demonology to Molten Core and they still have an intuitive, easy to learn rotation as their foundation. Destruction, particularly with the removal of RoF simply punches the keys as they come up until resources are filled, it's not a matter of simplicity vs complexity, it's adding a reflexive mechanism to keep you awake on those long burn stretches.