There's a mass delusion in the industry that using Kubernetes has to be hard, grossly over complex, and is always wrong if you are not Netflix scale. Is the system as described by the author significantly less complex and better than a small Kubernetes system? Sounds like they went through a lot of work to get it to their desired state.

Rolling your own zero-downtime deployments is as about as a good idea as rolling your own security... it's not a good idea.

I run our small system on a single EC2 instance with K3s. It runs a half-dozen or so services and does it quite well. I don't think it is particularly complex or over engineered. I like how easy it is to maintain the configuration in a helm package and quickly deploy it in different environments.

There is a learning curve for doing K8s well, but that's true for any non-trivial system.