Well, sorry, i'm mistaken, but only regarding PC's, which runs any C2 game really well. But for mobiles i still have my doubts...
Yes, you probably can't make a graphics-heavy game like that for mobile using C2 because WebGL effects can really take their toll on many phones. But you can make perfectly good 2D games like Candy Crush puzzle games or platformers or RPGs without the need to use almost any effects and make them run at a steady 60 fps on devices that are pretty low end by today's standards. I'm working on a puzzle game with large-scale graphics and pretty complex mechanics and testing it on my 2 year old 4-core cheap Samsung with 1 GB of ram and it runs perfectly well.