TL;DR: This is a seriously good movie and you should watch it. I was tempted to give this a 9 initially, because the movie is rather centred around just one theme, to the point that it can get monotonous. But if you like the manga or the anime, this movie does justice to the content.
Well, let's be clear about one thing: This movie is an ode to Kyojuro, the pillar of fire. From the very first notes of Kyojuro's theme, we know what will happen. The theme is at once heroic and mournful. It gives the listener the sensation of someone struggling at a Sisyphean task, one that they may never overcome. Even without reading the manga beforehand, I could have predicted what would happen to Rengoku. Despite this, the movie does justice to his character development, starting with the old woman who was once helped by his father and ending with his parting words. Everything about Kyojuro screams a fiery personality, like a person who lives his life as if he's 'burning the candle at both ends.' Akaza hammers this in even more with his repeated attempts to bring Kyojuro to the demons' side, and even tells him that in just 2 years or so he could have refined his skills further. We watch a heroic young person stand for his ideals, and that always leaves a lasting impression on people.
This can, however, leave a bad taste in the mouths of some people. We expect hard work and struggle to be rewarded. Despite his immense sacrifice, Kyojuro loses the battle because Akaza flees the scene after mortally wounding him. I felt as frustrated as Tanjiro watching the fleeing demon. If you're a fan of the manga, you know why this has to happen. You can fit this in the wider context of the struggle between humanity and demons and you appreciate the work the team put into this single arc. If you don't take a wider perspective of the plot though, this whole movie feels like an amazing build up to a war that never materializes. I think some of the reviewers who point out a hollow feeling upon watching this movie may be struggling with this. But this arc is very impactful and important in the wider context of things. People will just have to be patient.
This movie has other things going for it. The dream world sequences and the fight against Enmu were thrilling. We see a bit more of the Breath of the Sun move set, and I was excited by it. Enmu is an interesting nemesis. His blood art is terrifying and Inosuke and Tanjiro have to come up with smart ways to overcome them. The fight scenes and music are excellent. Akaza's theme felt slightly off-putting, but not to the point that it ruined the experience.
So, yes, there are some flaws with the movie. It can be a dealbreaker for some people. But remember that this is a shonen anime and approach the movie with that mindset. If you do that, this movie will not disappoint. It feels a lot like the Marineford arc in One piece, or Avengers: Infinity War. For sticking to it's themes so faithfully and executing it to the best of its ability, I think it surely deserves a 10.
