Howling:My Problem with Twelfth Doctor

Somethings bothering me. In the original timeline, the eleventh doctor died on Trenzalore and the time lords never gave him more regenerations. However what happened to all the evil that still needed fought? All of the adventures and enemies the twelfth doctor onwards will face was never defeated/done in the original timeline. So what happened? Was there no evil? Did someone else start defending the universe? Did the universe become a darker place without the doctor? Obviously all this peril will be stopped by the twelfth doctor and later ones but again, what if he wasn't there? What would happen? The same can be said for if the first doctor never left gallifrey. A cosmos without the doctor scarcely bears thinking about....