The kind of people who has to both set the cluster up and keep it up and also has to develop the application and deploy it and keep it up etc is not the target audience.

K8s shines when the roles of managing the cluster and running workloads on it are separated. It defines a good contract between infrastructure and workload. It lets different people focus on different aspects.

Yes it still has rough edges, things that are either not there yet, or vestigial complexity of wrong turns that happened through it's history. But if you look at it through the lense of this corporate scenario it starts making more sense than when you just think of what a full-stack dev in a two person startup would rather use and fully own/understand.