For anyone taking this the wrong way, I'll frame it differently: My OS has my structured and unstructured contact data (including their relationships with me and to each other), a way to attach contacts to calendar events and notes, and a standard API that apps can use (at my discretion) to access that data. How does Monica use/improve on that?

Monica seems like a pretty pedestrian contact management app to me. I’m struggling to see what’s impressive about it over, as you say, my iPhone, or, say, Notion.