Korra's romance is virtue-signalling because it was a tacked-on, barely touched-upon in the show, and adds almost nothing to the characters or the dynamic. All that stuff is saved for the comics, after the fact. It's shallow and only seems to be done for shippers, and the creators have been gleefully exploiting the pairing just for that.
Marcy/Bubblegum has more chemistry and build-up to it, along with a history. But they're the anti-Korrasami: they took over the show in various ways, their characters changed too much for the romance. It feels like the romance was revived because of the positive fan reaction to it, because it gets more and more focus. It's like giving a child ice cream for dinner instead of proper food: you know that the kids will like it, but it's not good in the long run and it's not helping.
Ruby and Sapphire are a middle ground: they're a couple that's not defined by the other, they don't steal away the story (aside from the occasional episode focused on them, and the Reunited arc.) They have problems and they don't always work through them, but they're trying. They're annoying characters, but that's because of their personalities and not their relationship. The relationship was always there, and their romance wasn't just included to look good, but to build on Garnet and explore the lore. It's just that once Garnet is revealed to be a fusion, her being two lesbians stacked together becomes the crux of her character. She's reduced to being fusion and lesbianism. The show is pandery in general, but you should have known what you were getting into. It's what panty shots and harem anime are to weebs.
One Stormy Night is explicitly about the friendship/romance of the characters and how it affects them. The movie is about selling you on the relationship, rather than creating it because there was a demand. And the relationship tied heavily into the characters' stories and the main plot.