Some of my thoughts coming back, crossposted from SB.
First off, I'll say that what I actually had hopes for, Joaquin Phoenix turning out a good performance was dashed. Phoenix is a great actor, but either he didn't care for this part or was handed a terrible script. He comes off as more like Arthur Fleck from Joker than Napoleon Bonaparte. He plays the part as an awkward, shy, weird dude who whispers or whines out half his lines. There is no indication of any charisma or larger-than-life qualities in there whatsoever. The Napoleon of the movie might talk (more like whine) about his 'destiny' or 'will' on occasion, but he more seems to blunder upwards than actually have any drive, ambition or initiative of his own.
He's also way too old for much of the movie - it's incredibly weird seeing a film try to fit the entirety of Napoleon's career in a runtime that's maybe three hours to begin with, and seeing a man in his fifties playing a fresh-faced captain at Toulon and then looking the exact same at Waterloo, decades later is just ridiculous. There's not even really an effort to hide it with makeup - the only changes he undergoes are clothes and a haircut.
But maybe Phoenix's performance is this way because of the script and direction rather than being the actor's fault. The film really fucking hates Napoleon. To an outright comical, even embarrassing degree. No matter what, it will go out of its way to paint him as a pathetic loser. This is most obvious whenever the British appear. Early on, the movie has Napoleon encounter the British ambassador, who proceeds to OWN the Corsican Ogre with his STIFF UPPER LIP. The ambassador looks on in passive dignity while Napoleon rants incoherently about how the British think they're so great because they have BOATS. And of course, once the uncouth Bonaparte pouts away into the distance, the unflappable ambassador cracks an one-liner about what a shame it is that such a great man has no manners.
At Waterloo, the impression you are given is that the only reason Napoleon is even alive is that the British are merciful and have a sense of fair play. A British marksman (complete with anachronistic sniper rifle, it even has a scope) sees Napoleon and tells Wellington that he can nail him - only to be rebuffed, because "generals shouldn't shoot at one another". See, Wellington is such a gentleman that he gets not only a physical, but also the moral victory over Napoleon. Bonaparte is defeated before the armies even clash. He only made it to the battle because his enemies are better, more chivalrous men. Then at the battle itself, you have the infamous scene of Napoleon leading a cavalry charge. It was actually something that made me wonder while watching the film. Clearly, the movie has no love for its subject. But how does that square with the seemingly over the top heroics of the trailers? Well, here's the answer - it's the set-up to paint Napoleon as being a loser, once again. He charges into the fray, then while one of his men (not Ney - none of the marshals are named in the movie, but he steals Ney's words) talks about watching how a Marshal of France dies, Napoleon's hat is shot. He is terrified by this, and leaves his men to die, retreating from the battlefield, the camera dwelling on this cowardly, pathetic sight through Wellington's eyes.
Afterwards when they encounter one another at the HMS Bellerophon, Wellington (Told to watch his head as he approaches because he's tall and Napoleon is short. It's funny, haha) sees him talking to a group of enthralled ensigns. Napoleon is of course pettily complaining about how his Marshals are incompetent and lost him Waterloo, and one of the officers observes that the ensigns seem quite taken with the emperor. Perhaps in another film, the impression you might get is that this is a nod to how people continue to be impressed by Napoleon's accomplishments to this day, but in the tone of the movie, it's clear that the answer is rather different - only children could possibly be impressed by this petty loser. Even at St Helena, he can't catch a break - the final shot of Napoleon in the movie is him insisting to two little girls that he burned Moscow, only to be corrected that it was the Russians who did so, in order to repel him. (The movie makes it clear that Napoleon is scrambling to get some credit, because we see Moscow burn in the film and he has nothing to do with it)
It's a fairly consistent pattern even outside the masturbatory depictions of the British. At the coup of Broumaire, we see Napoleon do a literal pratfall. He gets mobbed, runs away in a huff and falls down two flights of stairs. Naturally, the film dwells on his marital troubles, because it's another way to make its protagonist look ridiculous. He abandons the Egyptian campaign because he discovers that Josephine is cheating on him. He leaves Elba because he reads a newspaper which says that Tsar Alexander seduced her. The Italian campaign is skipped over entirely, but we have room for awkward sex scenes which mostly are there to show him as being bad at sex. (Why this is relevant is quite beyond me)
If the message being "NAPOLEON BAD" was not clear enough, the film ends with a scroll telling you how many people were killed in the Napoleonic Wars. (Ironically, in a film that reaches so hard to make Napoleon look bad, not a word is said about Haiti or Spain. Even more ironically, Marengo is included in the "NAPOLEON BAD" list despite the film telling you "Italy" surrendered without a fight)
This is not to say that you can't have a more negative depiction of Napoleon. But the problem here is, that the movie's notion of Napoleon being bad seems to be that he hates Britain for its BOATS and that he has no manners. No attempt is made to meaningfully engage with the man, the good and evil he did, or the implications of his legacy. Rather than grapple with Napoleon as a person, it tries to cheapen him by making him into a ridiculous, pratfalling caricature.
As a movie too, it's just hopelessly muddled and confused. It's very apparent that trying to cram a life like that of Napoleon into a 3-hour movie was a mistake, because while the movie has breadth, it does justice to nothing it portrays. It's less a story and more a series of incidents, only very loosely tied together. The film is about many things, but it does nothing well. Is it a battle film? Not really. The battles are small, short and unimpactful. Austerlitz is less than ten minutes and bears no relation to the actual battle. Is it a character piece? Maybe, but not a very good one. Napoleon's psychology is not meaningfuly examined because the movie is more interested in making him look like a loser. Is it about Josephine and Napoleon's relationship? That's probably the clearest through line I could detect, but it doesn't tell you anything interesting about either person - Napoleon is obsessed with her but we're not sure why. Josephine often seems more like she tolerates his existence than anything else, then shifts to liking him and being hurt that he divorces her. There's no meaningful development for either person.
And the film doesn't really have any characters at all besides that. Napoleon's marshals are wholly absent from the film - the only time the word 'marshal' is uttered is at the Bellerophon, when Napoleon complains about them. Characters enter and exit the stage without introductions - I certainly had no idea who most of the people in the story were, because they just don't have names and are rarely ever introduced. Francis and Alexander appear, but have no discernible traits beyond being obstacles for Napoleon. Wellington only appears at the very end, and has nothing to him beyond being this unflappable tower of British dignity and badassery that ol' Boney cannot hope to match. Talleyrand is sleazy, in this rather generic fashion of speaking in a roundabout manner, for the two or so scenes that he features in. Napoleon's family besides his mother are pretty much absent. You get nothing from the soldiers, their hopes, dreams or any thoughts - they're just generic spear carriers. (But unlike Homeric heroes, the protagonist of this movie has nothing interesting to him)
Compare this to Waterloo, a film from over 50 years ago, with no CGI to speak of and much more limited technology available to the production. Waterloo manages to tell a tight story, with stirring performances from its cast. It established characters, and showed us what the people participating in the battle might think. It had beautiful cinematography, with battles that put anything released since to shame in terms of actual, real scale (there were 15,000 costumed extras involved), and scenes that look like period paintings in terms of color and composition. Rod Steiger even managed to convincingly portray Napoleon late in his life as an imposing figure, declined from his golden years, egotistic and stubborn, but still energetic, intelligent and charismatic, the kind of man you can understand people followed across Europe, unlike the awkward, whiny loser that Phoenix portrays. You even get a clear picture of tactics, the back-and-forth between the commanders, or the bravery of the soldiers. It shows that you can do a great movie, while also keeping to a good standard of historical accuracy.
Stick with that, and don't waste your time on this film.