By working properly I mean the teams became better as the time passed. We maximized the both business and user value.

DevOps was part of each team, we had a setup where the team could function autonomously, meaning that all skills were available to reach the goal from the beginning to the end.

However, I can connect to what you said. If the DevOps is left apart many disappointments will happen. Retrospectives become a complaint about DevOps capabilities.

As I said, I've seen working, but I've also seen horrible scenarios.

Everyday I take as an opportunity to learn. But don't get me wrong, I am not a Scrum purist, I am passionate about team work, I believe Scrum is good on that. But Agile Manifesto is a guide for me everywhere I have been to.