Come on, North Korean regime exists for 70 years now and it is relatively stable. You're not going to heal the world. China will continue to do whatever it wants in Tibet and Cental Asia. The only thing you get by doing interventions against the regimes you do not like, is encouraging other countries to do interventions against the regimes that they do not like.

You can nudge tyrants into becoming milder and perhaps transitioning power sometimes in the future, and that would also have a benefit of not starting civil wars and having refuge crises.