I think it depends on how you can use the techniques right on the street. I don't think WTF TKD is useless on the streets. In fact, It was very useful at least for me. Just don't act as you were sparring in the street fights. Be smart and use lower kicks and also punches. If you're smart enough to change WTF to fit your style in street fight, it will be very useful. But if you want to learn the martial arts that teaches a lot of useful techniques in the street fight, i don't think TKD is the best choice here.