I think I get what you’re saying. The reason I like Key romance, especially my favorite Tomoya x Nagisa, it’s because it isn’t just pure romance. The characters, much like real people, have problems in life that they must face and they face them with the support of each other. This is exactly why I believe that it sets a goal of what romance should be. If characters were only defined by their relationship then I believe that either A, they’re too attached and fail to have a healthy relationship, or B are one dimensional. So at least in my favorite example, Key romance is actually better than others I’ve seen. But I only really, really have paid attention to that couple when I think about my opinion on relationships.
