It thought it brought the entire series together perfectly.
Unlike many others here, I never got around to watching the series until much later. The Pandemic has given me a great opportunity to catch up on long-running shows I had missed, and Deadwood was at the top of my list. I fell deeply in love with the show, all the characters, and all the actors. I hated the way it ended abruptly with the third series finale. But as far as I'm concerned, the movie brought all the story lines (the important ones, at least) together in an incredibly satisfactory way. I do not feel the need for more, which is what a satisfying finale should do. Of course, there was some tragedy, but that's to be expected in a great work of art like this.
My ultimate review is, it was PERFECT for what it was meant to do ... round off this great story in the best way possible, after a passage of 10 years or so. It was absolutely magnificent the way the 13 years between the end of the series and the release of this movie was almost precisely the same as the passage of time played out in the movie.
Bravo to all concerned, especially Ian McShane and Timothy Olyphant, both for their wonderful portrayals, and for producing this film.