Retrospectives don't help when your problems are external and you do not have influence on them. If you get how much needs to be done and what needs to be done set fixed from outside the team cannot do much about it. And that what scrum often ends up in a lot of companies: all the responsibility when things go bad but none of the autonomy that would be needed.
I've noticed a related effect, where every problem discussed in a retro has a "process" solution, because the team's own processes are the only thing the team can fully control.
This can lead to both a constant churn in processes and a piling on of additional processes, which bog the team down with an explosion of on-call-like rolls that get rotated through team members.
