When to not do Scrum
If your work is perfectly plannable and predictable: don’t do Scrum.
If you do not want empowered teams: don’t do Scrum.
If you don’t want to disrupt your organization or upheave your organizational structure to empower teams: don’t do Scrum.
If you want an exhaustive set of rules to follow and do not want to figure out what works for your context: don’t do Scrum