Each human has a power ceiling/floor. It’s the combo of their strength, leverage, efficiency in movement, ability to stretch, torque, twist, turn, etc. Some folks are blessed with easy power. Others have to make a very concerted effort and still likely won’t match others. The saying “can’t teach power” is a nod to guys who have the easy power and don’t need to spend as much time on that deficiency as another player would. It takes less time to get to the finished product if they can spend bulk of training time on pitch recognition and contact ability.