It ls based on the westward expansion of America, a period that is covered to death in media already.
It presents no unique or compelling twist or angle on this in the trailers.
It presents not amazing visual that can only be enjoyed in a theater instead of watching this at home like the History Channel.
I like Kevin Costner, I like westerns, I like history. I pretty much am the target audience. But when I was it was going to be at least 12 hours of content spread over the next 2-3 years, and I still had no hook as to why I should watch this over The Last of the Mohicans or Tombstone or any number of narratives in similar settings. It all feels incredibly low energy.
And this isn't even mentioning being stuck in an expensive theatre for 3 hours, that the show in its full is perfectly bingeable over a weekend and that there is a high likelihood that it might get cancelled midway through, which will really sting with a 4 episode mini series.
The fact you described it as "the show" is absolutely the problem in a nutshell. This isn't a film, or a film series, it's a fucking commitment. At least with Avatar, they're years apart and the most visually stunning graphics on the planet. Or with LOTR these are epic stories and sagas.
What is the saga of the American rancher Mr. Costner? I need to understand.
I figured it was about the mobile company, similar to the Blackberry movie. This makes more sense. And from the comments, it doesn't sound terribly interesting.
It's made by a Coen brother just not the ones you think. Mel Brooks' real last name is Coen and he is the younger brother of the others. He adopted "Brooks" when he broke into directing so he wouldn't be accused of riding his brothers coattails to fame.
Because it's not that good? A reviewer I like said it felt like the first couple episodes of a TV show stitched together with not much of an ending beyond setting up the planned sequels
On top of what everyone else has already said, I'd add that (for some reason) when it comes to Kevin Costner, movie-goers have long long memories about his "ego" projects like Waterworld and The Postman.
Costner went through a phase where he felt that he was big enough to direct, star, and write huge epic films because he was the "only one that could do them right". And that flopped his career...hard.
He went on from there to do a lot of smaller stuff that was really well regarded. But now he comes back with this, basically another ego-project, because he's convinced that Yellowstone has given him all of that old cred back. (It hasn't)
Dude is just Neil Breen with a budget, and people are rightfully still skeptical of any so-called epic that is written, directed, and starring him.
In short, Costner's epic movies have all pretty much been laughably bad with the exception of "Dances with Wolves". And Pepperidge Farms remembers that kind of thing.