I've worked in these types of organizations before, and it's always counter-productive to making positive changes in the environment. You as an SRE can either make it better, or find an environment that's conducive to positive changes.

If you'd like an outside resource to suggest or read up on better postmortem practices, the Google SRE Book has a chapter [0] on postmortem culture. It's an amazing change of pace and a huge stress level improvement for us SREs.

[0] https://landing.google.com/sre/sre-book/chapters/postmortem-...