If you read this section, the author gets a lot of things right, but clearly doesn't know the space that well since there have been people building things along these lines for years. And making vague commentary instead of describing the nitty-gritty doesn't evoke much confidence.
I work on one such language/tool called mgmt config, but I have had virtually no interest and/or skill in marketing it. TBQH, I'm disenchanted by the fact that it seems to get any recognition you need to have VC's and a three-year timeline, short-term goals, and a plan to be done by then or move on.
If you're serious about future infra, then it's all here:
https://github.com/purpleidea/mgmt/
Looking for coding help for some of the harder bits that people might wish to add, and for people to take it into production and find issues that we've missed.
And not only because of legacy systems that are hard to migrate to a modern platform. At my place of work there are workloads that can easily run on Kubernetes and it would be wise to do so. On the other hand there are systems that are not designed to run in a container and there is frankly no need to, because not everything needs to scale up and down or be available 100% of the time at all costs.
I think configuration management systems like mgmt (or Ansible and Puppet) are here to stay.
I think there is even a widening talent gap where you can't get people excited about doing something that maybe should have been done years ago (assuming VM -> containers makes sense for a thing). The salary needs to go higher for things that are less beneficial to the resume.
The industry at large asks most developers to stay up-to-date, so it starts looking suspicious when a company doesn't stay up-to-date too. For C# in particular, companies who have only recently migrated to .NET 5+ are now a red flag to me considering how long .NET Core has been out.
In the latter case I would consider it a red flag if some long-deprecated tool turned up in the tech stack of a company, but there might be perfectly good reasons to stick to the former, a bunch of VMs, instead of operating a Kubernetes cluster.
I ran a small Kubernetes cluster once and it turned out to be the wrong decision _at that time_. I think I would be delighted to see a job ad from a company that mentioned both (common hypervisors/VMs, containers/Kubernetes) in their tech stack. Without more information I would think that company took their time to evaluate their needs irrespective of current tech trends.