
you're not wrong. singing is something at stake. but at 13 years, the priority should not be changing societal standards of vulgarity. if this were more realistic, her opinions wouldnt be considered with her age and sex. it's not realistic to prioritize religious viewpoints over murder. it isnt logical. she's just bringing more attention to her family, making more reasons to be a target....

Are we reading the same story??
She is changing the standards of vulgarity, because the shame used by the temple was a way to control people, that's why all those people died.
How could the folk songs be illegal for any valid reason? They're expression of one's self. The reason why they were made illegal is because singing about anything else besides the hymns that praise the temple and what it stands for could undermine the temple's power.
No real antagonist is also untrue, we get minor antagonists sprinkled in because the biggest problem isn't one person, it's the controlling world the heroine lives in.
And I'm not sure whether I should even justify "fruitless protagonist" with an answer. Just because she isn't bubbly doesn't mean she's boring. She holds herself to a high standard and doesn't let anyone trample over her. Normally in these stories the male lead would come out of nowhere to save the mc, but she stands her ground. She's witty and cunning.

your points aren't wrong, but, in my perspective, music and singing should not be her main priority right now if she aims to immerse different culture and undermine the temple. her methods are unrealistic. i call her fruitless because her acrions and responses are predictable at this point, not because she's not "bubbly." her character does not live up to the potential she displayed in earlier chapters. it's fruitless because there just doesnt seem to be any more growth for her anymore. she's always gonna be that witty kid that one-ups everyone around her and nothing can stop her because this is her story.
the antagonist part... yes there's minor ones, but they were used as a ploy to emphasize the lead's intelligence and shit or wring up more drama.
the story lost its logic
The main character's favorite thing in the world besides her family is singing, she was in a horrible world where the only out was singing, the songs she sings are at risk of being illegal and her damn power is singing.
It's a story about singing and the wit of the heroine, not a cheap quick love story that will make your heart jump because of overplayed cliches.
Don't get me wrong, I love those stories! I read them over and over again and live watching the main characters fall in love at first sight, but for the love of god, could you people not compare those quick fluffy stories to stories with actual plots?
There are stakes here, the heroine main struggle isn't "this is an arrenged marriage, but i like him?!(´ε` ) ", she watched her country go into ruin and all of her family die. Don't read Lady Baby, The King and his knight or Yeon Lok Hein if you want a cheesy love story. The slow pace isn't a bad thing, the focus on the heroine's journey instead of her romantic feelings isn't a bad thing and the fact that it'll take a long time for the proper romance to come isn't a bad thing!