And did you know? “Romantic” almost literally means “like something out of a freaking storybook”.
People got romantic notions from reading romans (French for “novel”, as in roman a clef), a noun that etymologically derives from a verb meaning “to narrate a fantastic story" (though amusingly, its literal meaning was closer to “to say something in French”.) Such tales often included the finding and/or losing of love, but that was not what was meant by romance, originally.
You can go back through European literary history and find all sorts of stories called romances (a romance of this, a romance of that) that are focused on everything but love. A typical romance was more likely to be one part travelogue and one part adventure story, hence the early sci-fi genre of “planetary romance”.
When Jane Austen said that she doesn’t write romances, she likely meant that she didn’t write sweeping tales of grand adventure, not that she didn’t write about love and passion and relationships.
This is one of my favorite types of linguistic shifts, where a word has completely changed in meaning but its “new” meaning can apparently be supported in reading most primary sources that use the old meaning. I mean, just think about any old timey story you’ve ever read where someone scoffs at the “romantic notions” of a dreamer who reads too many books. Does the scoffer mean they have unrealistic notions of idealized love, or that they spend too much time thinking about “adventure in the great wide somewhere”? Or does it work either way?
(Cf. “protest” in “the lady doth protest too much”; at the time it meant to advocate for, the exact opposite of “contest” as a verb, but the line reads fine even with the meaning completely inverted.)