There already are a number of platforms that make deploying and operating apps very simple! Heroku, AppEngine, Lambda, so many others.

Your 5-person startup does not need a DevOps engineer. Your 50-person org should start thinking about it. Your 500-person company probably needs multiple DevOps engineers -- having every dev team independently figure out how to handle things like deployments, reliability, and security is chaotic and wasteful. There are a lot of details that only start to matter at scale, and both Kubernetes and dedicated infrastructure teams are for this use case.