Ensemble cast

I've been thinking so much about ensemble casts and what that means, versus I suppose a book or show that's about one or two main characters with the rest as supporting or less prominent characters. I'm not really sure I understand the difference, especially in a novel. But I can talk about the one I just wrote, which had three truly main characters and a lot of important but secondary characters, plus a bunch of tertiary characters without whom it would have seemed like an empty environment. The Esker Road has Becca, Zeke, and Owen as main characters. Shea is more of an inciting incident of a person and someone who knows secrets. He's sort of a bonehead and not really interesting to me or anyone else. He plays a role, an important role, but he's not someone whose head we get inside. So he's not 1 or 2 but more 1.5. Secondary characters go on for days. Erica, the roommate. Aaron. Pax or Paz. (Must decide.) Eleanor though she's so underdeveloped. Harriet and...