The MC is using his power inefficiently. Things will change the moment he realises he doesn't need to transmute stuff to be used against his opponent. He can just transmute the opponent themselves. It's far more horrifying. For example, there's no need to make the floor capture the opponent by having the opponent's feet sink into the floor or making the floor form a cocoon like in this chapter. He can simply fuse the enemy's feet with the floor. When the bones of the foot form one solid structure with the floor, no dude is simply walking away from it.