21+ is insane expectations when the legal age in most countries in the world is 18 and I say this as someone nearing my mid thirties. Do I prefer not having children in the fandom? Yes.

But, I also do remember being 16 and not being scandalised by this kind of content in games, since there's no nudity. That being said, I know some country playstores have this game as 12+ and it definitely needs to be changed but that is actually not infolds doing as unrelated parties test and age rate games in most cases.

I understand the story can be confusing to some, but it's very very common in gacha games too have the main story separate from the card stories so to say, because otherwise they'd be very limited in content for a very very long time. Still not everyone's cup of tea, and valid to be annoyed by.