It's another Chaplin silent comedy. Is it funny? First half no, second half yes.
Importantly, it has a plot. The funny stuff (for me) was all tied into this plot, while the stuff that didn't make me laugh was just Random Comedy Business that could have been dropped into any film. What's more, by "plot" I don't just mean "framework for the gags", e.g. "Laurel & Hardy go on a picnic". Chaplin's written a character-based story with emotion and the most striking scenes in the film are those that demand proper acting.
So, what is this plot? It involves a double role for Chaplin and it starts with the filthy rich. Edna Purviance (of course) is the neglected wife of Drunken Chaplin, in a dinner jacket and a top hat. Chaplin doesn't reel, hiccup or otherwise play him as drunk, but we can tell he's not right because he's forgotten his trousers. This leads to embarrassed antics that are mostly unfunny, but do get amusing when he steals a newspaper and starts doing a Dalek impression with it. (Yes, I know Daleks didn't exist in 1921. That's still what he's doing.)
Meanwhile Purviance's character isn't even meant to be funny. She's trying to do the right thing for a drunkard husband who's more interested in alcohol than in her.
That's one Idle Class: the rich. However there's another Idle Class: the Tramp. My word, he's appalling. He's an entertaining movie character, but in real life you'd be building electrified fences to keep him out. He's callous to the point of cruelty. He's a girl-chaser. His natural state is running away from policemen. You can see all this and more in the golf sequence, in which the Tramp makes people cry and gets them beaten up. I've no idea why the Tramp wants to play golf, but he does and so the film becomes an unrelated movie that you can imagine as "The Tramp Is Mean To Golfers". This is indistinguishable from a silent comedy set-piece, except that it's not funny and instead is a bit disturbing.
After that, though, we get back to the plot and the film improves.
Chaplin's two characters (Drunkard and Tramp) will get mistaken for each other, of course. The most striking scene is one in which Purviance is sitting next to the Tramp under the impression that he's her husband, no longer drunk and instead having come downstairs to be with her. Neither actor is doing anything. They're acting. It's a level of filmmaking you'd never have expected ten minutes earlier when watching the golf. Similarly my favourite Chaplin moment in the whole film is the way he simpers when protesting that he and Purviance aren't married (because he fancies her).
There's still lots of visual comedy, but this time it's meaningful because it has character context. Drunk Chaplin getting stuck in a suit of armour is funny. (It's a fancy dress party, which explains why the Tramp was accepted by a bunch of toffs despite wearing his usual clown shoes and a suit that's probably been dragged behind a truck.) The Tramp's approach to fist fights is funny, i.e. lying down pre-emptively when he thinks he's about to get punched.
Overall, it's impressive. I'm not a fan of the first half, but none of it's dispensible because the Tramp will meet his golfing partners later at the costume party. The second half though would be a strong and entertaining silent comedy even if didn't have that character work between Purviance and Chaplin that raises it to a level beyond its peers. What's more, it's almost as if Chaplin's deliberately undercutting his sentimentality. He has a cruel streak too. He can fool you with apparent sentiment, then undercut it with his cynicism or childish vindictiveness.
Laurel & Hardy are childish but sweet and their comedy runs on stupidity. The Tramp's comedy runs on selfishness, irresponsibility and shameless bad behaviour... but that's only the starting point. Chaplin can then change gears to another level, both in terms of the Tramp's characterisation and in terms of his storytelling as a writer/director. I definitely need to see more from this guy.