Elinor does "esteem" Edward greatly. They say that love is blind. So, she feels the need to justify Edward to Marianne and to herself, as well.

At the same time, I think Marianne underestimates Edward. He does not match up to her idea of a hero from a romantic novel. So, she is already predisposed not to like him too much, and therefore, I think she does not even try to appreciate his taste and his manner of reading.