If you are focusing on Customer First, then you are focusing on the wrong thing

If you are running a project, then you use Project Management as the method. If you run multiple projects, then you run Program Management as a method. If you run continuous deliveries for a product or service, then you use product/service management as a methodology.

If you write code in either of those, then you use whatever method you want that fit whatever framework you have selected. Your work is the same, and it is only the level of detailed requirement and time restrictions that are different.

If you estimate correctly, then the management format should be irrelevant for you. If you can't estimate or work with requirements, then projects will feel like hell on earth and most likely fail.

This is not rocket science and if you want to be really good at your work, make sure you become an expert in working in project format because continuous deliveries will automatically be easy at the same time.

Don't blame projects for your lack of competence in estimation and working with requirement in a fixed delivery setting. Learn it, or continue to let everyone involved to suffer.

It really is that easy.