It's because the people who dis it, likely fear it. They would never attempt to participate in Olympic Taekwondo because their skill is not good enough or they don't have the knowledge. Instead they can make snide comments about it and give all kinds of bravado reasons why they won't try it and never will, it's a cop out. You never see them put their money where their mouth is. Most I find are weekend seminar warriors.
I think that a lot of people simply don't know about how fast and powerful competition kicking is. I have students who also train in BJJ and like to do local MMA tournaments. The kicking we find from MMA players are short (just like most taekwondo practitioners), they don't put their hip or weight behind the kicks and so their kicks end up being about the same fighting distance as their punches. So they can kick and punch in combination quite well from the same distance.
Our strategy is to kick long, off the line, to their front leg, and two or three of those and they are wincing and weakly lunge in because they don't want to get kicked anymore. That is fine with us, because we are comfortable with the ground game as well. Or if they try to punch, it has little or no power because they cannot torque off their front leg (bashed in) and end up in a back weight stance, raising their front leg to defend. Then comes the knock out with back kick or spin hook kick, as we fake to the leg and spin when they flinch up on their back leg. So by taking away their kicks, we take away their punches as well, and the fight becomes two ranges, our long kicking distance, and ground.
Afterwards, they always comment, what kind of kick was that? And when they hear "Taekwondo", they gain a new respect for something they thought very little of just a few minutes earlier. Kicking is not something you can just read a book or watch videos and get. You really need a good teacher to explain the how, when, where and why.