I’ve seen quite a lot retrospective summaries. Usually a great reading. In vast majority of cases they were clear proof that someone put a lot of work in. You know, gathering information, discussing, looking for methods of improvements and finally writing down the whole thing.
Good job. They should get a medal or something.
Except it was complete waste of time for everyone who was engaged.
It is still a very common situation that retros are done as we were taught but only to the point when the summary is written down. Then people call it a day and go home in sense of the job well done. The trick is they don’t learn a thing from the exercise, which means the whole effort was futile from the very beginning.
So don’t bother with retrospectives. Unless you plan to do anything about problem you find, that is.