Because God is beyond all human understanding, we can only use via negativa. It was counter productive to speak of God as if he could be encountered by senses
It is impossible to understand. Only saying what something is not gives no indication of what it actually is. Someone could be thinking of something entirely different which happens to have the same properties. You'd have to be extremely specific
Via negativa aims to describe God by using negative terms to say what he is not. This avoids misleading claims about God’s nature. For example, if one was to describe God as Father, we would view him as a human because that is what our idea of Father is whereas God is a metaphorical Father.
Example Paragraph of Via Negativa A01 2/2
PseudoDionysius said that via negativa was the only way in which we can speak truthfully about God because he is beyond all human understanding and we should think of him as a mysterious being that cannot be interpreted by our senses. If we say what he is, we deny God the sorts of qualities and limitations that might apply to other beings