I am reading Karen White's book, Agile Project Management, A Mandate for the 21st Century. She uses the term adaptive problems to describe the types of problems our projects are meant to solve. I've see this term used before, it means our problems can't be solved by our traditional tools; we have to adapt out tools to meet the specific problem. Applying our standard approach just won't work on the complex problems of the 21st century.
This can apply whether your using agile or a more traditional approach to your projects. If you blindly follow a standard approach, you may be creating problems rather than solving them. We have to admit that we don't know the answer and be willing to learn as we progress through the project.
I've seen this with one of my clients. They were following agile and all the ceremony associated with it. They had their stand up meeting, iteration planning meeting, and even their retrospective, but I didn't see their approach evolve as the project progressed. The retrospective became a thing they had to do, because the methodology said so, but it wasn't helping them learn and adapt on the project.
So where do you draw the line? You don't want to throw the baby out with the bath water; abandoning the things that are working, but you have to be willing to adapt and fix the things that don't work. This is where you need to be a leader and help the team adapt while focusing on delivering the value your project was undertaking to deliver.
For example, if you are measuring progress through story points and you drop in the number of points you deliver from one iteration to the next, you need to figure out why and adapt so that next time you deliver more. So how are you helping your team evolve today?