By casual I mean like Call of Duty casual. I'd like to separate shooters into 3 categories: 1. Hardcore - Counterstrike 2. Kinda hardcore - Battlefield 3/Halo 3. Casual - Call of Duty series I'd like to think of MNC as a game where anyone can pick up and play, but also a game with a steep learning curve. You can play MNC and do decently without focusing too much on the meta but you can also do better by learning the game and it's glitches, techniques and tactics.
The only class that takes decent aim in MNC is Sniper. The "shooter" emphasis in regards to skill level is low. It's more of "Don't be an idiot and do what your class is supposed to do"
I'd go with "kinda hardcore". I definitely don't think anyone can just hop on a be good in this game since theres too many match ups and playstyles to learn. If you have a competitive backround then you can probably pick up the assault right off the bat. Although it doesn't have spawn traps, weapon times, and set ups like halo, it's very high risk and reward gameplay, and with juice buying off, it leaves out the random/luck factor. I had a lot more fun playing competively in MNC than in Halo 3, and I played a **** ton of the halo series.