That's true, but a lot of Cain's atrocities would have occurred even if she was bombarded with riddles and visions. Raiding civilians, murdering her XO... those things occurred very early on.
And they were done in sight of the greater good. To misquote a very great man, a guilty conscience is a small price to pay for the safety of the human race.
Cain made some wrong choices but she was under an insane amount of pressure and for all she knew was protecting the only existing humans. She couldn't afford to be soft.