They Came Together is a skewering of the tropes that make up the modern romantic comedy, and there are a lot of reasons why it runs so smoothly. For one, it does a great of job casting, since Amy Poehler and Paul Rudd are both people that could headline a legitimate rom-com, but they can also go more surreal and over-the-top when needed. It also helps that the movie's script has a variety of jokes and doesn't merely riff on how contrived romantic comedies are, which would get old quickly; They Came Together throws in a lot of absurd tangents and inspired skits in with it's parody elements so that you never know quite what direction a scene is going to go in. But the main thing that makes it sing, I think, is that it's actually pretty insightful about what makes romances work and what makes them fail.
As I was watching They Came Together I started thinking about how romances have evolved over the decades. When you look at older movies, they tended to go to one of two extremes: either they would either go completely into fantasy or they would stay completely grounded. Roman Holiday, for example, went all in on glamor by setting the movie in an exotic location and casting the impossibly graceful Audrey Hepburn in the lead. In contrast, Gone With The Wind has some fancy elements - particularly in the beginning before the war - but is always grounded, because Scarlet O'Hara's romantic problems can't be solved with a heartfelt speech, and when the war breaks out her love life has to take a backseat to basic survival. Some of those old romances have a Hollywood sheen to them and some of them aim for realism, but it doesn't seem like they mixed those tones very much.
However, modern romances often try to split the difference by putting someone "relatable" into a magical circumstance. The main characters will have problems just like normal folks do - job troubles, a squabbling family, an inability to consistently stand up, or whatever - but then the rest of the movie will take place in fantastically nice locations and the plot will be are set into motion by unbelievable coincidences. The mixture of those two tones doesn't really make sense; the characters stop being relatable the instant their lives get taken over by unrealistic contrivances. (That is assuming they were ever relatable in the first place - it would probably help if they cast people that looked like normal people in these movies but they don't.) These films are too magical to be realistic and too focused on being about people like you and me to be glamorous.
The jokes that worked the best for me in They Came Together were the ones that were riffing on the many strange ways that rom-coms try to establish someone as relateable and how alien those characters actually seem. Amy Poehler found a way to parody the klutziness that rom-com women are often burdened with - which is saying something, because falling down is meant to be funny already, but something about her crazy eyes while she's flailing around pushed the gag to the next level. Watching her flail around I had to think: it is really weird that someone decided that the best way to make a female character look human was to make her be unable to enter a closet with hurting herself.
At one point the happy couple goes to meet her parents and it's revealed that her family are white supremicists. Yes, that joke is in large part about the awkwardness of meeting the folks, but it's also reminded me of how rom-com parents are always kooky but in a toothless way; as side characters they are almost never allowed to have more than one trait, and whatever trait they get has to be quirky without being alienating. Rom-com in laws are a specific type of awful that is so finely calibrated that you would never be able to find it in the wild. But hey, they have wacky parents just like us, huh?
The rom-com has been suffering in the last few years, and I get why; the genre got mutated into this weird beast that was neither fish nor fowl and was kind of unplatable to anyone with common sense. But there is another thing that They Came Together reminded me of: underneath all the gimmickry of the modern romantic comedy there's still a sturdy structure. They Came Together cast two likeable, funny people in its lead roles and watching them flirt and goof around was really enjoyable. I don't think there will ever be a time when a movie about two charismatic people being charming together wouldn't be worth watching, provided that the filmmakers made up their minds about what tone they wanted and then stuck with it. We as a people can come back together with this genre; I think we're just in the awkward middle part of the story where there's been some miscommunications and hurt feelings, but we'll probably reunite in the end.