Well, I hate to say it, but versus BJJ or Judo, TKD fighters usually don't come out well. And I'm not talking about MMA, I'm talking about someone who only knows TKD versus someone who only knows BJJ or Judo (I'm not sure about Aikido) and the TKD fighter usually loses. I honestly can't think of a single YT video where a pure TKD fighter comes out on top against a pure BJJ/Judo guy.
As for the only kicks thing, that comes from complete ignorance, and for the fact that TKD has become infamous as a kicking art. But ironically, TKD has more hand techniques than it does kick.
As for being able to say that BJJ sucks because it only revolves around grappling techniques... well, grappling techniques have proven their effectiveness. Most of TKD's fancy kicks have not. And I'm not saying this to say that TKD is useless, it has a lot of good principles and techniques. But as a whole, I do feel like grappling arts are more effective than striking arts.
And yes, I have learned this from personal experience. I have very fast kicks and punches, with a lot of good power and accuracy and timing. And I studied TKD for about 2 hours every single night of the working week, and competed in local tournaments. As a black belt in TKD who trained religiously, I had my first encounter with a BJJ blue belt back in 2001. And as we were sparring, for the life of me, I could not prevent him from successfully clinching me and taking me to the ground. No matter how many times I would spar him, it would be the same thing, over and over. He would clinche, and no matter how long I was able to hold him off, I would eventually get tied up and taken to the ground again. Now luckily since I had 6 years of wrestling under my belt, I wasn't helpless on the ground, but the point was that I was considered very good at TKD and was a black belt. And I still couldn't prevent a blue belt in BJJ from getting the best of me.
And furthermore, I watched all the UFCs up to that point. I remember seeing the stand up fighters getting taken down and I always thought, "Yeah, well that guy sucks, but they can't do that to me!" I even remember one of my instructors making fun of the stand up fighters for not being able to prevent the grapplers from taking them to the ground and said they were idiots. And yes, many of them didn't look too great, but then again, I also learned for myself that had that been me, while my techniques would have looked better and I wouldn't have looked like a slob, I would have shared the same fate as all of those guys.
So that's when I decided to start MMA training and have been ever since.