If we judge it contextually—and by what it presumably sets out to do—Midsommar is a successful addition to the 'folk horror' genre, much as Hereditary was.
On a 'creepiness' continuum, with Luca Guadagnino's 2018 remake of 1977's Suspiria being, say, an 8 or 9, I'd plot Ari Aster's Hereditary at 7 and Midsommar at 6.5. (And for what it's worth, before I forget, I'd place 2015's The Witch at an 8 or so. Great film; super creepy.)
Both Ari's entries on this continuum are sinister, but I will say that Midsommar achieves something spectacularly unique because it's so dang rare these days: With nary one single jump-scare or cheap boo tactic (think Annabelle-anything by James Wan), and in the gleaming brightness of endlessly sun-soaked 22-hour-long summer days no less, Midsommar conjures such ominousness, foreboding, plodding 'predatoriness,' and outright dread that one must tip his hat to the writing/directing auteur at the helm of this Viking ship of a film.
Aesthetically and artistically, by the way, it's flat-out gorgeous.
Folk horror—relying as it does on paganism, simple/rural/ancient rituals, isolation, and dark, lingering forces always felt yet rarely seen—is very hard to pull off. Whereas Hereditary had a high school, spooky backyard, tree fort, funeral home, multi-tiered/multi-doored residence, and an attic to leverage, Midsommar occurs almost completely (more than two hours' worth!) out in the open...in a stunning, bucolic, Vail-like alpine meadow in Hälsingland, some four hours by car north of Stockholm. Sure, there are a handful of interior shots filmed in rustic wooden outbuildings, but very, very few, and virtually none of which play a prominent role whatsoever in comings, goings, or happenings of any essential sort.
Like David Blaine's 'close up street magic,' I find this impressive, even if I'm not otherwise moved by it in any memorable way. #Respect, if nothing else.
I will confess that despite all these amazing accomplishments, however, I personally found Midsommar to be a bit of a letdown, insofar as it's (arguably) much ado about nothing. Nothing happens, but also...literally nothing happens. I don't think 'atmospheric mood' is quite enough to carry a film, however saturating and enveloping its vibe may be. (I absolutely LOVED Sigur Rós's beautiful, haunting 2007 film, Heima, for example, but I knew going in that it would be mostly the equivalent of massage mood music and modulated my expectations ahead of time. Midsommar aims to be a cinematic story, and I guess it is, but gosh/also, it's kinda not?)
But wow, in other news, the origins and impacts (seen and unseen) of eons-old cultures, customs, taboos, mores, norms, and notions of family, fertility, life, sacrifice, and death itself are powerful and mighty, however hokey the hoodoo.
My own opinion, such as it is, is that we NEED films like this periodically, if only to remind us how important the light and hope and bread of life.
I suppose in the end, my advice would be to #pass, but if you remain desperately famished for something unusual, welp, I know of a tiny, funky, weird, Shyamalan-like Nordic hippie Village/commune that'd absolutely love to have you swing by to smoke their psychedelic shrooms, drink their dirty spirits, and dance an entrancing jig 'round the old oak tree.
If you do, don't bother intending to tell me afterward that I didn't warn you beforehand. You won't get that chance.