Romance is the icing on the cake. It's a fancy garnish to help them draw out certain ideas and subtleties of the bigger story. Like, for instance, I'm pretty convinced that they put the Clexa and Wicken scenes right next to each other to highlight how both girls are coping with their emotional pain. Not because the show is secretly all about love and there's some deliberate plot against Bellarke. They'll do Bellarke when it has the greatest capacity to be meaningful to the larger themes of the story.