I wouldn't say Karate is useless in a real fight situation. Keep in mind that there's a difference between competitive fighting and real street fights. Though street fights are far more dangerous, the level of skill you encounter is far lower. Just because you can't land a reverse punch on a good boxer doesn't mean you wouldn't catch some asshole at the bar right on the chin.
I get what you mean though, and I agree completely. What good is a gun to a blind man? How useful is the five finger death punch if you're not used to landing shots against a non-compliant person that's intent on beating you to a pulp?
But that's why you cross train. You learn some dangerous techniques in _______ and you learn how to land techniques in Karate.
The techniques in karate arent suited to a street fight. I'm not going straight to the stomach outside the nightclub, but through sparring you gain a lot more fight knowledge. My mate actually got started on by a few travellers in a pub a few weeks ago. He said that they were insanley slow after we spar in karate. Out techniques are so much quicker, both through training and the actual techniques themselves, that he only took one punch to the back of the head when three guys were swinging at him.
And yeah I like the cross training because each martial art poses a new challenge. Karate is very different to my style. I get asked "Did you used to be a boxer?" every night in the class haha, but it's good to test yourself in the things you struggle with. In the other class, I have to use elbows and round techniques (punches, knees and kicks) which can be quite difficult to do in comparrison to the standard roundhouse kicks in karate which again can be a challenge.
TKD opened up and had my karate sensei not already sworn us off of it I'd head over there too. TKD is a very good style to have messed with when you are younger because it opens up a lot of striking possibilities when meshed with other styles. Muay Thai is a lot easier to impliment into MMA than TKD because TKD requies so much technique and ability where Muay Thai can be a lot easier to pick up through a standard MMA class.