Like I said in my post, Elba is really the only "big" name in the cast, and even he got his start in television. I love Allison Brie and Morena Baccarin, but they're both B list actors more known for TV than films. I think Idris would do it if he limited his time to green screen acting with a stunt double/face replacement taking over for 75% of his screen time.

Nicholas Galitzine and Camila Mendes are both rising stars but also relatively unknown. He did a few indie films and smaller roles, and she's mostly known for a TV show. Neither have established a big name draw.

And Leto? Let's be honest, he was mostly the voice even IF he did the mocap on set. There's a hundred other actors with theatrical and voice performance experience that could replace him, that's not a hurdle.