The Ancient One

I have no problem with Tilda Swinton as the Ancient One. And that even if people shouted whitewashing, and even if it was a move made purely for financial reasons (China has become, in recent years, one of the main markets for Hollywood blockbusters).
The problem is that this character, who seems to be feared and respected by even Dormammu, didn’t concern herself with Kaecilius. She obviously has the power, and she has no problem with bending the rules (the whole natural order of things that turns Mordo into a villain). So why didn’t she use the Eye of Agamotto to turn back time and stop Kaecilius from stealing those pages?
Better yet, how was she killed so easily, even though she already proved that she could take on the villain and his minions with ease?
Come to think of it, Tilda Swinton didn’t have too much to work with in this movie. Which is a shame – given the controversy surrounding this casting choice. But I guess this is a problem for the entire MCU, with most of the time dedicated to developing main characters and almost no time at all for the villain and secondary characters.
