The events that lead to Ruto becoming a sage and having to remain in the Sacred Realm occur in a completely separate timeline than the one in which Link lives out the rest of his life. In his timeline, Ganondorf never comes to power, and thus the people who would have become sages in the alternate future are able to live normal lives. With this in mind, it certainly becomes possible for a relationship to occur. The same is true for any of the other female sages, as well. You’re free to like whatever pairing you wish, and I certainly won’t try to change your mind if you happen to think that “Link wouldn’t have accepted her,” but it is important to remember the facts when making an argument.