I sympathize with the author, and in principle I find myself nodding along with his prescriptions, but one of the benefits of Dependabot (and Renovate) are that they are language-agnostic. Depending on how many repositories, and how many languages, and upon whom the maintenance burden falls, there's a lot of value to be had. It may not really be feasible to add "the correct" CI workflows to every repository, and the alternative (nothing) inevitably ends up in repositories where dependencies have not been updated in years.

It's good optimization advice, if you have the time, or suffer enough from the described pain points, to apply it.