Exactly this.
I spend a bunch of time reading accident reports from agencies like RAIB and MAIB, but my real jobs have been closer to the Web PKI and thus m.d.s.policy
Back in 2015, Symantec's CA issued some certificates that shouldn't have existed, including for names owned by Google. What's wrong there? Well, a blameless postmortem would probably tell you that your processes and procedures are bad, you are creating bogus certificates to "test" a real CA whose certificates are actually trusted in the real world. Need better processes, training, oversight to ensure things improve. What did Symantec do when they were caught? They fired the low-level employees who conducted the tests and wrote a blog post "A Tough Day as Leaders" which blamed the fired employees for getting it wrong. Some leadership (the blog post of course no longer exists although I assume it's archived somewhere).
Less than two years later, Symantec is back in trouble again because an RA they've worked with has been issuing certificates, using their CA infrastructure (and thus, from our point of view they were issuing these certificates even if they unaccountably believed this isn't their fault) that should not exist. This time Symantec's bosses blame not only low-level employees, but also auditors, bosses at the Korean RA, and anybody else they can think of... except themselves.
This is a gross failure of leadership. Once upon a time a US President said "The buck stops here", but Donald Trump was very clear, "The buck stops with everybody" and "I take no responsibility" and it seems Symantec's leadership were made in that image. They quit the CA business rather than do what it would take to fix the problem.
If you conduct a "postmortem" after an incident, then "Nobody was to blame and nothing needs to change" is almost certainly just as much the wrong outcome as "It's Jane's fault, fire her".
I mentioned I read MAIB reports. One MAIB report sticks out, after many years, in the following way:
Unlike every other MAIB report I've read, this one has No recommendations. Someone died, and yet there is nothing to recommend. Why not? Well, the cause is very simple, two men on a fishing boat took a lot of heroin, and their boat crashed, it sank and one died. No need to recommend that you shouldn't take heroin while operating a fishing boat since heroin is an illegal drug already and operating a vessel under the influence of drugs or alcohol is already a crime too.
If your next "blameless portmortem" doesn't have any recommendations, ask yourself, was what happened already a crime? Are the people involved dead or in prison and so either way beyond the value of recommending a different course of action next time? No? Then we need to recommend how to actually avoid it happening again.