No resistance = no real technique. It's that simple.
"Martial" means having to do with or suitable for war.
And "art" means skill at doing a specified thing, typically one acquired through practice. If you aren't learning something suitable for combat through repetition, you are learning how to dance and punch the air. Not apply techniques in a life or death situation. The community needs to be aware that pure taekwondo schools in our world today will not teach you the fundamental skills for self-defense and how to fight. Sure it may look good in movies, but in the ring, on the street, ect. It won't work. There may be some schools out there however, that offer taekwondo in addition to other martial arts. But a pure taekwondo school would not do that for you.