The thing about Henry Tilney and Catherine Morland is that their romance is a deliberate subversion of the tropes found in those melodramatic gothic fantasies that Catherine loved reading and which Jane Austen adored mocking.
Some readers get upset that Henry didn't fall in love with Catherine immediately and that she fell first, but it's a deliberate jab at those gothics where the male becomes creepily hyper-obsessed from the millisecond he spots the heroine and she finally 'succumbs' only after he's worn her down. Similarly, the heroes in those gothics are dark, brooding, grim and stoic, while Henry is a delight, charming and funny and playful. The fictional heroes and heroines of Catherine's gothics have dark, intense dynamics, often dangerously attracted to each other while not even especially LIKING each other, while Catherine and Henry take strolls and chat amiably about books and develop a genuine friendship before even kissing.
Catherine's arc is about learning to dispel her unrealistic fiction-formed assumptions about life and love through actual experience. Henry is nothing like the fictional romantic heroes she's read about, yet the perfect man for her in reality.
And Catherine is exactly who Henry needs as well - someone who's as curious and eager to learn as he is, someone who genuinely enjoys his playful sense of humor rather than thinking he's annoying or condescending, someone who adores his beloved sister, and someone who genuinely entertains and surprises him with her vivid imagination and surprisingly insightful instincts. (Keep in mind that Henry himself acknowledged that Catherine's instincts about his father's character were completely on point - my girl just went a bit too far in deciding he murdered the wife whose life he made miserable!)
Most importantly, Catherine's filter-free candor and sweet sincerity cuts through the layers of irony and snark he's cultivated to protect himself from a dreadful home life and are a refreshing contrast to the phony interactions in 'society' that seem to have left him quite cynical and jaded.
I'm not saying anyone else has to like them, but I started loving and appreciating them even more when I realized that they're supposed to subvert the romantic tropes found in many romance novels (then and now!) in favor of the more quiet yet real love that Jane Austen and I believe is built to last :) And the fact that Henry's sister Eleanor was the one embroiled in a secret, passionate and forbidden "gothic-esque" romance the whole time is one of Austen's best winks to her audience.
