First of all, DC is primarily a detective fiction manga, Gosho said in one of his detective libraries that DC is only romantic on the side and wasn't really intended by him in this form (paraphrasing a bit here, but that's the gist of it). So, romance is just a bonus. Gosho is not a very good romance writer, true, but Shinichi's confession is one of his better moments in the series in regards to romance. Understanding what's in her heart, is more than just knowing that she loves him, you know? Other than that, yeah. Gosho doesn't put much effort into it, because it's not the focus of the series.