Instead, I loved it. I enjoyed almost every minute of it. It's pretty much the sort of experience I look to cinema for, and the sort of experiences that are the reason I'm into film in the first place. If movies like this didn't exist, I would mostly stick to other media.
I think there are legitimate criticisms of this movie -- I personally didn't like the ending, largely coming from a place that I disagree with Aronofsky's beliefs in a cyclical universe (that he showcases in The Fountain and Pi as well, so I know it's his thing). But that disagreement comes from the statements he was making, rather than the fact that he was wrong to attempt to make them.
As for what that statement is, if it isn't clear earlier, it's transparent by the time the frog bounces out from the blood-dripping wall that we're in allegory logic, the space where characters are types of energy and cause-effect is metaphysical as opposed to any sort of Newtonian rules-based system. The topic of that allegory is about as much about motherhood as Finnegans Wake is about a funeral; it's a reworking of the Bible the way Finnegans Wake is a reworking of Genesis; it's a rip-off of Rosemary's Baby the way Finnegans Wake is a rip-off of Tristan and Isolde; and it's a criticism on the egoism of fame the way Finnegans Wake is a criticism of alcoholism. Let this statement not stand as a comparison of QUALITY -- Finnegans Wake is incomparably better a work than Mother! -- but I use the analogy because too many negative reviews of this affix their criticism to only one track with complete dismissal of the others. But the whole is larger than the parts.
Where you go from there is a largely angry, exasperated, and fearful mood piece about the self-destructive and bestial behavior of human beings, with a question mark as large as the titles exclamation point about why God lets all that happen, and finally a bittersweet and sort of hopeful / cynical exhaustion over the idea that it all renews to happen all over again. Take from that what you will and experience the rest for yourself.
As for entertainment value, after decades of engaging on the subjects of tastes, entertainment, and escapism, I've learned I'm more at a loss than anything at understanding why brain-splodey headshots, squiddy toilet monsters, and cult rave raid battles fail the spectacle any more than space wizards, superheroes, and murderous clowns. I enjoyed just watching the movie, I didn't have to analyze it to fill the time of experiencing it. I have nothing I can offer there but vague platitudes about the unaccountability of taste and something about target audiences. If it's not your thing, I know I'm not going to convince you.
But there are two arguments against this movie that are invalid.
People are complaining that Mother! is too 'stylized.' Mother!'s camera is a forced perspective -- just to the side of POV (of which there are a few key shots punctuated about), the visuals of the movie reside entirely in the peripheral vision of the main the character. This isn't too stylized, this is something ONLY CINEMA CAN DO. You don't get that uncanny feeling of something just out of your vision in any continual protracted sense from any other medium. If that's forbidden from cinema based on your arbitrary rules of 'style', then cinema ceases to have anything interesting going for it. One reviewer who liked it quite a bit mentioned "It makes you desperate for a wide shot". Who else felt desperation? The main character.
People are complaining that Darren Aronofsky is pretentious. If only more directors were pretentious, so that we'd get these visceral experiences that sent the audience I was sitting with (sold out show, post-bad reviews and flopping news) cringing, gasping, groaning, gagging, and eventually tumbling out onto the street talking about it -- love it or hate it.
Pretentious is a movie designed only to sell toys claiming some universal meaning because it follows the beats prescribed by Joseph Campbell without reading the book to learn that the format is only the capsule -- meaning is the capsule's filler. Stylized is a movie throwing three layers of lens flare and grading firmly orange teal to avoid laying bare the overcoverage that allows the producers to undercut the director and DoP. Mother! was a movie made by a person's decision to risk it with a personal voice. I'd rather watch movies with a voice I hate than a movie lacking voice at all.