Skaffold's focus in on automating the build, push, apply part of the development cycle. Okteto's focus is on moving development to a Kubernetes cluster, abstracting away Kubernetes and the container from your inner developing loop. (I'm one of the creators of Okteto).
We started building Okteto last year because we found that the existing tools were focused on speeding up the kubernetes cycle, and not on the end to end flow. Our goal with Okteto and Okteto Cloud is for most developers to be able to work on Kubernetes-based applications without even realizing they are on Kubernetes.