I (controversially it seems from reading comments around the web!), really enjoyed the film. It looked and sounded amazing, the voice cast all did an absolutely incredible job and it more or less covered what I expected it to.
I don't disagree with the general opinion that the flashbacks and overall structure aren't great. However, I challenge anyone to consider how much of a slog it would be to have both the fights and flashbacks split across multiple episodes/weeks in a TV format. It's gonna take solid months to get through some of that, and by that point, we will definitely have forgotten what was happening prior. Even if they shift things around, I don't think there's any fixing the problems the source material has left us with.
I don't really think narrative threads from the first hour were abandoned, though. Yes, things with Doma aren't entirely settled, but at the same time, it did conclude the main objective there, and I'm happy enough for the story to loop back in the next film. Both the other two major plotlines were followed through to their conclusion, too.
Having said all of that, I am someone who has finished the manga for Demon Slayer so perhaps my expectations were better set since I knew exactly what we were likely to be getting here. ^^;