I miss the Scions too, but whoever we got in Dawntrail weren't the Scions proper. They were shells of themselves offering nothing more than any other character in their place would have because they were devoid of any personality with very little care to the growth they have had or their dynamics with each other.
The Scions currently have the same issue as whenever a Persona game gets popular and they start making spinoffs: all the main characters are just caricatures of their personality. They want the character but they don't want to mess with them too much so they make them have a few identifiable quirks and that's it. They don't want to use them but they don't want to change them so now their presence is just kind of there for fans when it should be for the story (imo).