Where to begin, where to begin....
Tell you what, I'll make it simple.
Let's pretend there are three movies:
1. The one you wanna take your date on. You know, for laughs and giggles or spooks and scares.
2. The one you wanna dig for art's sake. You know, for cinematography and such.
3. And the sort that's a thinker. You know, "What's the meaning of life, and why are we here?"
As far as #1 goes, well, Mother! ain't that. It flunks as a horror film, as a drama, and as an "entertainment" picture, because it's not particularly entertaining. I mean, kinda, in the first forty minutes, maybe, but only because their farmhouse is all kinds of Joanna Gaines cute and you're wondering what the heck Ed Harris and Michelle Pfeiffer are up to. You're thinking Rosemary's Baby.
As for #2, um, it's okay. I'm just not into that bouncy-cam/ER-vibe, where everything is filmed close-up and terribly realistically (!). It's claustrophobic and gives me a headache. I kept wanting to scream, "Just leave!" but, uh, that ain't happenin', so the walls close in pretty fast and you'll be inclined to exit yourself. And the FX aren't particularly impressive, which sorta shocked me considering it's ILM.
As for #3, yessir, it's one tremendous allegory, the roots of which I shall not spoil for ya. It's a bit misleading though—for the longest time—because you keep thinking, "This can't be what I think it is, because that is so untrue," but then you realize, "Yep, that's what's a comin'!"
It'll make you think, to be sure, but because Aronofsky plays pretty fast and loose with the allegory as I understand it, it's a mash-up. I think if he'd played it more truthfully, it coulda been mighty powerful.
As it is, yep, there is tons to ruminate upon, but there's also a lot that's inaccurate—and therefore misleading—which, allegorically speaking, feels like a cop-out or half-baked dodge.
When the credits roll, all your tumblers will fall cleanly into place. I was mostly bummed because I kept thinking, "If they are who I think they are, well, they're not as I know them to be."
Anyhoo, I hear that half the folks love it, and half the folks hate it, and I understand. You either love or hate Aronofsky; that's always been the case.
For entertainment, I give it a C- or a D. For art, a C+. For allegory, a B-, if only because he misleads you, rather than tackling the subject more truthfully.
But I give him credit: he makes one heckuva commentary, earning a Purple Heart for the wounds received in storytelling.