I'll agree with you on Mystique but not Magneto. He resolved things with Scott when he rejoined. He did with Xavier in Excalibur. He tried to make amends with the X-men, especially Kitty, when he brought her back from space. He also tried to work things out with Teen Jean and the other young O5. He earned the team's trust and remained loyal. Mystique on the other hand, never really cared. I think Emma and Magneto's tenures as X-men has been on a similar level.