WH was never a romantic novel in our modern interpretation of 'romance'. However, WH was very much in keeping with the beliefs held by the Romantic poets (who Emily Bronte loved) e.g. the superiority of emotion over logic, the reverence of nature Vs. the hatred of industrialisation, the idealisation of the innocence of children etc.
Cathy and Heathcliffe are at their best/purest when they are children, running wild across the moors, at one with nature and each other. It's only when puberty hits and they have to engage with the real world that they become 'corrupted'.
Adult Heathcliffe isn't a passionate, rough diamond with a heart of gold. He's a nasty, cruel bastard who beats up his pregnant wife and viciously slaughters her pet dog. He isn't in love with Cathy, he is obsessed with her and would prefer to see her dead than with another man.
Adult Cathy isn't a sweet, passionate, free spirit. She's incredibly shallow, selfish and self centered, marries poor Edgar purely for his money, and proceeds to be a hateful bitch to him. Cathy isn't in love with Heathcliffe, she just loves the fact that he is obsessed with her.
They are both horrible people who deserved each other.
It is Catherine Linton and Hareton who have the romance story of WH and who actually have some chance of a happy ending.