True. I'm currently in the middle of writing a paper on extending Kubernetes Scheduler through Scheduler Extender[1]. The process has been really painful.
You're saying a feature that's in alpha, released 2 months ago is painful? You should at least wait until a feature is beta until expecting it to be easier to use.
Scheduler Extender was initially released over 4 years ago[1]. What you are referring to is Scheduling Framework[2], which indeed is a new feature (and will replace/contain Scheduler Extender).
[1]: https://github.com/kubernetes/community/blob/master/contribu...