Sometimes there's value in building bespoke solutions. If you don't need many of the features of the off-the-shelf solution, and find the complexity overwhelming and the knowledge and operational costs too high, then building a purpose-built solution to fit your use case exactly can be very beneficial.

You do need lots of expertise and relatively simple applications to replace something like k8s, but 37signals seems up to the task, and judging by the article, they picked their least critical apps to start with. It sounds like a success story so far. Kudos to them for releasing MRSK, it definitely looks interesting.

As a side note, I've become disgruntled at k8s becoming the defacto standard for deploying services at scale. We need different approaches to container orchestration, that do things differently (perhaps even rethinking containers!), and focus on simplicity and usability instead of just hyper scalability, which many projects don't need.

I was a fan of Docker Swarm for a long time, and still use it at home, but I wouldn't dare recommend it professionally anymore. Especially with the current way Docker Inc. is managed.