I really like Jeff Gothelf’s approach to the question “Does every project need to be Agile?” in his newsletter issue Digital transformation is not innovation:

No. Every project does not have to be Agile. However, each project you work on should encourage and support agility. This means that every initiative creates the ability, desire and safety to change course in the face of evidence that contradicts our original plan.

He goes deeper on what it means for teams to have the ability, desire, and safety to change when needed.