The only time when we see the ideal of a marriage for love, from the beginning to the end of Wuthering Heights is when young Catherine marries Hareton Earnshaw at the end of the novel. Other than that, what we get is a continuous obstacle course between true love and the importance of social status, mostly starting with the first Catherine.
Although Heathcliff and Catherine love each other and share a form of cosmic connection nearly, the fact remains that Catherine clearly preferred Edgar over Heathcliff because she would become the richest woman in the county, and appearances mean more to her than anything else. This, however, is not a behavior inherent only to Catherine: It was the way society viewed marriage during her lifetime. However, we also can see that Catherine never respects the institution of marriage, as she openly demonstrates over and over that she still and always will love Heathcliff.
Similarly, Heathcliff ends up marrying Isabella, Edgar's sister, because he would become the sole heir to her estate once Edgar dies, or she dies herself. He does it as a way to avenge the marriage between Catherine and Edgar and, at the same time, remain close enough to monitor all of the activities between the marriage. He also wants to ensure that he makes them suffer like he, himself, suffered at the hands of Hindley plus the humiliation he received from Catherine's refusal.
Additionally, Heathcliff makes the young Catherine marry his invalid son just to take control of Wuthering Heights at the time of his son's death. In that time, the males took control of the wife's possessions at the time of marriage. Plus, what best punishment to Edgar than to have his beloved daughter marry the son of his nemesis, Heathcliff?
Therefore, Wuthering Heights is far from depicting the ideal love connection, nor the best love story there is. Even the young Catherine and Hareton seem to hate each before they make their ultimate love connection. All of the marriages are orchestrated to serve a specific purpose, and marriage is only seen once as a conduit for true love.