Sure, you could interpret Lewis' treatment of Susan as sexist. That is easier than figuring out how Lewis could really object to her being SENSIBLE.

And you could imagine that Susan's exclusion is permanent. That is easier than coming to peace with the fact that the friends of Narnia died, and those who were not friends of Narnia lived, giving them more time to become friends of Narnia once more.

Let us hope Gerwig does not take the easy road.