You need to be careful with ideas of the ancient world and some kind of universal mother goddess or creation goddesses. In terms of one’s own personal belief, well, that is entirely up to the person and it is his or her right to believe what he or she wants, however, in terms of historical fact and genuine ancient traditions, there’s not a lot of evidence to support this view and plenty to counter it. Most ancient traditions have some kind of primordial force of creation and the gods and goddesses come later and, of course, the Celtic peoples seem to have lacked a creation myth entirely!
One thing that ancient peoples did seem to focus on in many traditions was the power and magic of words, and this may have been a reason why the druids who the Greeks and Romans encountered did not commit their lore to writing, not because they couldn’t – they used writing in many Celtic areas – but because by having the knowledge of names and words, you suddenly have access to this power. This idea of the power of the word is found in Egyptian, Judaeo-Christian, Greco-Roman and many other traditions. Perhaps, it’s also why the druids spent so long committing stories to memory and it could explain the importance of the bardic tradition too.