While this is technically true, using old, unsupported versions of software (such as etcd) in production is a recipe for disaster, especially when you start running into problems with it.

I think, in the case of etcd, it would have been better for the k8s folks to fork the project and add whichever features they felt were needed to be able to use it for k8s. Instead, it seems like they swarmed the original project and added a ton of features that made it a behemoth of complexity rather than the simple tool it once was.