My professional experience tells me that the next question will be who decided for B given Y, then you answer it and then you have a target on your SRE back, I'm afraid. Remember that the trickle-down economics works only when the shit hits the fans and what trickles down is not money.
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.
Where are all of these managers out there running companies making decisions with literally no thought whatsoever? I've literally never seen them- I almost exclusively work with rational human beings who are able to justify decisions, and the few who aren't haven't been afforded any real power.
Mostly legacy industries. I don't want to indicate it's common. And typically gets weeded out by Director-level.
But I've certainly seen more Top50 companies than not who have at least a few Manager / Sr Manager-level folks, in charge of key teams who own the sole keys to necessary functions, who are happy to say no to anything they're ignorant of, without any impetus to learn about it.