I did taekwondo when I was little and I know some people who still do it. All martial arts are technical once you get into them, but grappling is different from striking in that what you do with your body is very similar to following a decision tree. Eventually these decisions get internalized into your muscle memory, but there's still a high degree of "if he does A, I'll do B, which will leave me open to C and D, which I can counter with E, F, and G, etc". Basically getting better at grappling involves filling out this decision tree.
Striking arts operate at a much faster pace so you really can't do that, the depth of the decision trees are much shorter, which is why I think bjj is more analytical and appropriate for most HNers.
I don't want to get into a flame war, but I personally don't find taekwondo and karate to be particularly realistic to fighting. Everyone has different motivations for training though, if you enjoy the fitness and athleticism of those arts, go for it.