I beg to differ. Yeah, it's true that a lot of Martial Arts moves are too complicated to preform in a fight the same way you do during practice. But years of practice can give you the reflexes to perform a lot of the proper techniques during a fight.
One of my friends got in a fight with a black belt once and guess who won. I guarantee you my friend didn't fight fair, but he lost anyway. And a lot of Martial Arts classes don't need to be belt factories. In the class I am taking, when it is time for a test, you pass based on knowing the Material. If you don't pass, you still owe the testing fees. Therefore a belt factory would benefit more from not passing you, so that you have to pay for the same test various times.
Muay Thai would be a very good Martial arts to use for a fight, add some striking classes and some grappling classes. The UFC has proven that it is effective. Also, the Gracie family has proven that Brazilian Jui Jutsu is more effective in a fight than karate.