"Great" by comparison to whom? The arts mafia likes to lionize people that align with their socio-political agenda irrespective of their actual ability. Examples include Dorthea Lange, Annie Liebovitz, Sebastian Salgado, Ansel Adams, and Sally Mann. That's not to say they were not competent photographers, just that their "greatness" was manufactured because they made the right politicial and social noises.
But Maier's work stands on its own - no agent, no gallery to pimp her work, no arts critics to make sure her work gets the nod - just the work on its own. That's remarkable in its own right.
Sure, it's raw, unorganized, unedited, and perhaps without full context, but at least the stuff I've seen, I think is superb. The lack of social and political filtering by a third party makes it so much moreso (clearly, she had her own social and political filters as we all do).
Full disclosure: I consider art in the service of commerce "advertising" and art in the service of politics "propaganda", and art in the service of contemporary culture "cotton candy". While each of these have created some occasionally lasting good work, it's rare that any of them have any real durability. Art for its own sake and only for its own sake is much more precious and rare. The truth is that because it is so hard to make great art, people resort to the aforementioned as a sort of short cut to try to become relevant, important, famous, influential, rich etc.
Oh, and Artists Statements are the height of self importance wherein the artist attempts to insert themselves in front of the art. Let the work speak (or not).
My 2 kopeks worth. YMMV. We can all still be friends.