My interest is piqued

Saw the trailer, and I think it has the potential to be weird and interesting!

Or it would, if they'd cast another lead actress. Portman tries hard (and it shows), but she just gets less interesting with the passing of time.

so lots of modernist and post structuralist nonsense?

It's not a bad movie, just a very unpleasant one.
The "young" segment felt very standard. The credits / ambulance sequence was ghostly and very fast, and matched the later story about Celeste's recurring dream. But after that, everything played out first like a BBC school shooting documentary, then like a teenager-in-adult-world sequence.
We get to hear that Celeste's connection to her sister was deep and significant, then one scene later they are cold with each other and full of drama.
Then grown-up Celeste is a horrible person, and I have never quite noticed so far how screeching Portman's voice is.

It was not bad to have (one more) look into the crazy world of showbiz which turrns artists into crazy people, but there was hardly anything new here.
Still, I may have seen a bit more clearly now how hard it must be to live in a world where everybody thinks they are entitled to a piece of you. Makes one appreciate anonymity a bit more, that feeling of navigating a social environment as if it was just another part of nature, just another background. It must be quite horrible to have the background trying constantly to interact with you. But this was still not unique, and Celeste was still not someone with whom I'd like to spend any second.

So here I am, being mean to a piece of art, which is (a very small) part of the reason why people like Celeste turn into bitches and drama queens. Imagine being not just observed, but judged all the time, coldly and carelessly - must be part of the reason for her breakdown before the concert.
And then again, art survives through judgment, it exposes itself and tries to generate reactions, without which it would be nothing more than our high-school poetry at the bottom of a drawer. And exclusively positive reactions would have pretty much the same effect as no reactions.
So I'm afraid that this negative criticism is nothing but a part of a game.
I understand that this movie involved a lot of work and dedication, but, well, I didn't like it.

It's better than Corbet's last film. Natalie Portman is very good in spite of her own character's inconsistency. The girl playing both her as a teen and her teen daughter later in the story is also good.