This is a great perspective on where DevOps comes from and what it is, however I have to disagree with you on a couple of points:

First, while I don’t think that you should ever think of hiring a DevOps engineer as a magic bullet to say you are following DevOps practices, I do think that the title of DevOps Engineer has meaning. A DevOps Engineer has expertise in the kinds of tools and automations that can enable a development team to be more productive and reduce bottlenecks. A good DevOps Engineer is also an advocate for DevOps culture and practices, who will help guide you down the path towards DevOps Nirvana.

Second, I take issue with the idea that everyone should have profound knowledge of the system as a whole. This puts an immense burden on everyone and means spending much more time than necessary on onboarding and continuing education. Instead I would advocate for a services-based approach, where people take responsibility for a small number of services that they maintain. Using this approach it becomes very easy to discover where a problem lies, and fixing issues is simpler because the responsible party has a very deep understanding of that service.