I love that last paragraph!
I think the Celtic triple goddess did exist. It/She/They certainly appear in some very old manuscripts.
You have many place names in Ireland that refer to Ainne (maiden aspect), Grainne (mother apsect), and the Callaigh Berra (Hag aspect). You have places like the Paps of Anu (my what a pair of hills those are!).
I just don't see any evidence of a global 'One Mother Goddess'. Many female goddesses yes, all with similar motherly traits yes, but the same being/entity no.
I'm just a killjoy :-)