The importance of the Arian heresy is that it makes Jesus either semi-divine, or divine by adoption, or divine by birth (rather than divine since the beginning of time). If this is the theological position one adopts, it means that he ceases to be seen as the sole means of access to the "Father" (the Divine Source in Neoplatonic terminology), because if he is a son of God, rather than the Son of God, then there are other sons and daughters. And this quickly leads to Unitarianism - the belief that the Divine is One and can be accessed by reason and intuition, and does not require revelation to be known. That's not to suggest we can fully know the nature of the Divine, but we can see it reflected in the world around us, in other people, and the beauty of the universe. It also means that if we are all children of God, then we all have the potential to develop our inner "Christ" / Messiah / Buddha / Enlightened One.
I wonder how different the world would be if the Arian heresy had won out at the Council of Nicaea.