One of the most frustrating trends in romance is the "passive protagonist"—usually a female lead who things happen to . The love interest sweeps in, solves her problems, and defines her existence. This is not romantic; it is parental.
When we move away from "perfect" characters and embrace "perfectly human" ones, the romantic storylines become infinitely more compelling.
When you pursue extra quality, you stop asking "How do I get these two people together?" and start asking "Why do these two people desperately need each other to grow?" The moment you answer that second question, your romance ceases to be a subplot. It becomes the soul of the narrative.