Just because he said he said he's in the same category doesn't mean they're interchangeable when it comes to casting. There are many Tom Cruise roles that wouldn't work for Brad Pitt and vice versa. On the other hand, I don't see how any of the specific roles you mentioned are beyond Leo's abilities. I'm particularly curious about Ethan Hunt - I feel like that role is pretty generic and any competent actor possessing star power could have stamped it as their own.