what is the importance of the basic ballet dance positions?

As an example the heart move relies on the shoulders for the reach and precision. The Swan is all about arm definition, nobody will be looking st your legs

Balance and centering, preparatory to movement.

They are tha basics for a reason.  Ballet is a core for all dance.  Everything you’ve ever seen is just an expansion

It is the base of all other steps in ballet.

The ballet positions simply allow you to start of a ballet move properly. For example, before you do a plié, you have to put your feet in first position. (Heels together; feet turned outward) I don't know if you've heard this or not, but people often say, "ballet has a right and a wrong, no in between." And if you don't start off with the correct position, it's all wrong.