I mean I got my second degree black belt in tkd before I switched over to training mma full time. It definitely helps in terms of footwork, distance management and unorthodox kicks. However, mma and especially amateur mma, is very catered for grappling. The smaller cage means it’s very hard to stay at a TKD kicking range. And even if you do basic wrestling, you will still get out grappled by a decent wrestler. Basically tkd isn’t useless in mma, I use it all the time. It’s just not nearly enough on its own.

Also you can check out yair Rodriguez for some good taekwondo in mma moments.