A Doctor of the Church is, by definition, a saint who was a voluminous writer/preacher on morals and theology. This isn't critical of +ABL, but his background wasn't theology, was it? Did he even write 1 book? I would classify him as a "missionary" type of saint, not a theologian. St Francis of Assisi (one of the greatest saints ever) isn't a Doctor of the Church, but that has nothing to do with his sanctity, just his office/purpose in serving the Church.