Switching from Jenkins (supposedly self-hosted) to Github Actions (cloud hosted runners) is faster? Impossible, any self hosted runner is bound to be faster than any standard-size Github Actions runner.
But you can self-host github actions runners as well.
Devex is about picking the "right" tooling, which sounds obvious and generic, but it still seems like not everyone get what that means.
As long as you've thought far enough in the future, you'll be fine
The article makes the point that developer experience has more to do with the organization they work in and the culture (advocating a culture of writing) than in just the tool chain.
Seems reasonable. I like the focus on the team and their needs over the new and shiny. Also nice the action items are few and concise.