Why wasn’t Origen, the most prolific writer of Christian antiquity, canonized?
Origen (185-254) was born in Egypt. In 230 he visited Palestine and was ordained. Much of his teaching was condemned during and after his lifetime, so few of his many writings remain, except as quoted in the works of other writers.
A chief reason for Origen’s non-canonization is that he believed in the apokatastasis, which is the idea that in the end all people and all angels, even the fallen ones, will return to their pristine spiritual state. They will end up in heaven, though after much purgation. In the end, hell, if it exists at all, will be empty, and everybody will be saved. It was a fine theory. The only thing wrong with it was that it was untrue. Our Lord repeatedly taught that hell exists, that Satan and his minions are there, that some (even many) people will be consigned there, and that it will last for all eternity.