Salva nos, Domine.
Saying that the Catholic Church fell into grave error suddenly is saying that Christ failed to protect his Church, which is saying that Christ failed, which is impossible
Matthew 16:18 And I say to you, that you are Peter, and upon this rock I will build my Church, and the gates of Hell shall not prevail against it.
Matthew 16:19 And I will give you the keys of the kingdom of heaven. And whatever you shall bind on earth shall be bound, even in heaven. And whatever you shall release on earth shall be released, even in heaven.”
Sola Scriptura is flawed.
Matthew 16:18 And I say to you, that you are Peter, and upon this rock I will build my Church, and the gates of Hell shall not prevail against it.
Indulgences freed you from the temporal results of sin, and donating to the Church was charity