Why did Pope Innocent III not become a saint?

Innocent III was one of the most powerful and influential popes, considered to be the most powerful person in Europe at the time, but in some respects far from leading what we would think of as a saintly life. He is regarded by Roman Catholics as one of the greatest popes of the Middle Ages, and by others as one of the most harmful men ever to have lived. It is said that both claims have merit, and both may well be true. Himself a "nephew" (a term that often meant illegitimate son) of Pope Clement III, Innocent III had a nephew who would one day become pope as Gregory IX. (Gregory's own "nephew" would one day become Pope Alexander IV). This would scarcely have raised eyebrows in Rome during the Middle Ages - in fact any cardinal or pope known not to have a mistress or two might have risked being considered homosexual.

Policies that would be to his discredit are his institution of the medieval Inquisition, the Albigensian Crusade against the Cathars and his condemnation of the Magna Carta.

Pope Innocent III was a very efficient and powerful leader. Even those that disagreed with him admitted that. However, those are not the qualifications that lead to sainthood. One must also lead a life of heroic virtue and Innocent did not.