You're really big on absolute statements, aren't you?
I bet if you're a pretty big guy, doing Crossfit will make you considerably less strong. There's a lot of cardio, which means a lot of room to lose muscle mass.
If you currently don't do shit, then yeah, sure, Crossfit and all of those other programs are probably great. But just because you "use muscle groups" doesn't mean it's going to make you stronger and fitter.
Then again, I'm talking to the guy who thinks Paleo is the pinnacle of all diets.