Basics are the key
Think of basics as the foundation of your Taekwondo and martial art. At white belt level the majority of your training is pure basic technique and your learning is very technical. As you progress is it very easy to concentrate more on power, speed, advanced techniques and reaction times. Revisiting your basic stances, basic formations and techniques helps remind your body and brain what you should be doing.
It is very easy for students to forget the Taekwondo tenet of humility and think they are too higher grade to basic basics, this is totally incorrect. By not practising you will be become rusty and forget. Basic training is also extreme hard work as you can’t hide behind flexibility, speed or power. Your technique is stripped raw so work hard on your basics and it will pay off in everything including poomsae, one-step, self defence and even sparring and full contact fighting.
Remember: A good analogy of the importance of basics is comparing them to that of a house. It a house doesn’t have good foundations it will eventually fall down, the same with a martial artist, without your basics you will not become an excellent martial artist, there will be flaws in your technique.