Perhaps the question shouldn’t be what is THE moral of love and romance on Once but what is A moral of love an romance on Once? I don’t think there is any one moral of love and romance on Once. It isn’t one size fits all.
Here’s the problem: if Adam and Eddy don’t have a moral behind their own story, in their eyes, and they are leaving it up to fans to speculate then that’s incredibly bad storytelling. The author needs a message, even if it’s one I disagree with. That’s fine, I can disagree with their message all I want, but yes the author should have an understanding and a clear vision/message behind their story.
Yes everything is text and the “author is dead” but the author still has a voice, it’s just not an omniscient voice that existed before the text. Adam and Eddy do not seem to have a moral for love and romance on their own show. That’s problematic.