This is a loaded question because of course there’s going to be some level of lust that occurs between two sexual beings based on their physical appearance.
[Were the story using asexual beings a la Good Omens this would be different, but still incredibly valid as a romance.]
That being said, looks don’t define attraction; they are merely one sliver of it, and an ethereal sliver at that since looks change as we age.
[Again, this would be different were I to write about a society where aging doesn’t occur the same way.]
I think it’s a cop-out to say “it depends” though that is the most real answer to the question. Some characters are going to be more hyper-focused on physical features—with each being attracted to different types of people—and others are going to lean more toward the non-physical, the actions a person takes, the personality under the skin, etc.
It’s more fun to have a range of different types of characters when writing novels, otherwise they begin to feel like the same story told over and over again. This extends to how the romance is sparked—whether it’s a first-sight lust that drives the characters originally, or whether the characters need time to come to appreciate one another.
There are two important things I think need to be touched on in a romance story:
One: There needs to be at least some level of physical attraction, unless the character is asexual. [However, I will likely keep asexual characters to my short stories as of now rather than my novels.]
Two: The relationship needs to grow beyond physical attraction so that the characters have a reason to remain together once the story is over.
Those are the not-very-hard-and-fast guidelines I think about when crafting a new romantic relationship. So, on a scale of 1-10 of how important a character’s looks are, it starts slightly higher at the beginning of most romances and scales down as the characters learn to love each other, faults and all.