Romantic subplots are a common part of pretty much every genre. It doesn’t matter whether your main cast is exploring a derelict spaceship, fighting a dragon, or toppling a dystopia. There will likely be two or more characters with a budding romantic relationship between them. In general, I would say I like romantic subplots in stories, but there are a lot of pitfalls associated with them.
A problem I’ve run into with romantic subplots I’ve read is when the writer doesn’t build them properly. There’ll be a few lines where the characters mention they find each other physically attractive and the writer will call it a day. I’ve also seen it where the writer will decide that two characters should be in a romantic relationship purely because they spend a lot of time together and are of compatible genders and sexual orientations. The writer then fails to put in the leg work in to make the relationship believable. Love at first sight is a nice idea, but falling in love with someone based purely on their appearance is a poor foundation for a long term relationship.
It gets even worse when the much more interesting main plot is ground to a halt or derailed because the protagonist is dealing with relationship issues, or when the main cast acts like two characters have a bunch of chemistry even though they’ve had like two conversations that were mostly arguments. The romance will be something the writer tacked on regardless of whether it improves the story. This is especially bad when there’s destiny or time travel shenanigans which make the relationship guaranteed.
Good romantic subplots are ones where the chemistry between the characters is well developed. It’s not just that these characters think that the other is hot. Their feelings have grown over the course of working together to deal with the main plot. They learn to understand and appreciate each other’s strengths and weaknesses while also caring for one another. Their personalities complement each other in a way that makes them almost feel meant for each other and they’re both better off for having met.
A good example of a well-done romantic subplot would be in the show The Owl House. The protagonist, Luz, starts out as enemies with the bully character Amity before becoming closer over time. This relationship works because they balance each other out and make each other’s lives better. Luz is outgoing and whacky while Amity is more straitlaced and organized. Luz helps Amity to tone down her overachiever tendencies and break away from her toxic mother. Amity, in turn, joins the main cast as a good guy and helps to take down the main villains. There are episodes focusing on their relationship and episodes where the relationship is more in the background while plot stuff is happening. It was, overall, a good way of mixing romance into the show that enhanced the main plot.
Overall, I think romantic subplots are a good way of adding an extra layer of conflict and complexity to the character interactions, but at the same time it is very easy to mess up. If a writer isn’t willing to put in the time and effort necessary to build a relationship between two characters then they should think long and hard about whether a romantic subplot is even necessary. Not all stories need romance to be interesting.