Video by myself above. What do you think of Taekwondo as a martial art? It has a lot of detractors. I think it has certain benefits at least for the sport of MMA. The bouncing they use for footwork can improve a fighters footwork. Improves your spinning attacks. Improves your flexibility for high kicks.
Like any art, if it's regularly and properly pressure tested, then it will work under pressure. Just like any other art, by itself it won't make a good all round MMA fighter, but taking the skills from it, filling your game out, and training in the correct environment for that goal is likely to lead to some success.
I think even as a just a striking art it's far too kick focused and not nearly focused enough on punching people in the face.
I like Taekwondo a lot as an art. I studied it for a long time, earned advanced rank in it, and taught for a long time. I don't like the direction that Olympic style TKD has gone... it's moving away from a lot of what I liked in TKD, namely the full contact sparring with limited targets that you had to hit hard to score. The electronic scoring and the rules changes have made it more a game of tag, and in my humble opinion, detracts from the application of TKD in a practical way. Yes, in a way... the footwork, kicks, full contact sparring, breathing, etc all have lots of benefits. That said, though, if I had a student approach me and say they wanted to compete in MMA, I would send them to an MMA school to train, not to a TKD school.