Romance in The Return of the Native is often not all that romantic or even nice. Love, for the bulk of the cast, is extremely painful. In fact, love is a fantasy for many of these characters. Characters fall in love based on their romanticized vision of another person, not on reality. And when reality comes crashing down, it's not pretty. Eustacia is blinded by her longing for Paris when she falls for Clym, while Clym blinds himself to Eustacia's real personality and desires. Meanwhile, both Damon and Eustacia seem bored by the idea of happy, conflict-free love. They clearly agree with Shakespeare's thoughts on how "the course of true love never did run smooth."
Diggory's love for Thomasin is the only honest love story in the novel – Diggory isn't blinded by his love, unlike everyone else.
Thomasin does not love Damon by the time they finally get married; she only marries him due to a lack of other options.