It's being worked on, Sync is a very mature app whose codebase had to be migrated over from Reddit's API. An MVP was prioritized over more advanced features like posting.
As a developer, if I was able to release what this dev did in the time they did it, I would be losing my mind. This person is obviously working like crazy (and in a very smart manner) to do what was done. You have to choose what to focus on.
The primary purpose for most people is to read, reply, and comment on posts. This is a good compromise for most people. For post creation, you have other clients until it is done.