This is like saying Mario games just involve running and jumping over holes and on enemies -- it doesn't do justice to the air control, to the momentum, to the moments where you skirt death and weave in and out of danger with lightning quick reflexes.
Likewise with RE6: As your enemies transform and swarm you, often in your blind spot (and in campaign, sometimes tracking you from a mile away), you have to be ready to duck, dive, roll and slide, to counter and quick-shot, to daze for melees and more if you want to survive with more than a few bullets and blocks of health, especially on higher difficulties. Pacing your herb-mixing and pill usage, tracking your surroundings while keeping up the fight, etc, all takes more skill than is evident when someone is "making it look easy." And that's why it's so satisfying -- it's accessible, but deep, easy to learn but hard to master. In Mercs, especially, these tactics are the difference between a high score and a low one. It's the delicate back and forth, like a dance -- action at its most addictive. I really rank this up there with Bulletstorm, Vanquish and Kid Icarus Uprising when it comes to pure action.
Again, my first impression of the game was terrible, and I wasn't determined to like it or anything. On a whim I tried it again, and found myself oddly compelled to explore it further, and then acclimating to its pace and learning its intricacies made it -click- like none other. Now I can't put it down.
