Put simply

What I believe about software development in simple terms:

If your team will not pair AND test, if your Customer will not prioritize, if your customer and developers will not collaborate, then nothing you are doing process-wise matters even a little
bit.

If you have these problems, you might want to forget your standups and scrum-of-scrums, scratch your code reviews, disband the QA team, ignore any promises about delivery. Better to spend your time collecting resume fodder.

If these are your problems then change your company, or change your company.