But you don't have to call it a demo.
It's an Alpha release, a release that doesn't have all the features of the full game and is typically tested by the developers.
You could also call it a debug build, a release for the purpose of finding bugs in the code.
Besides, your thread has the Developing tag, not Demo, so people won't necessarily expect something perfect but incomplete.
Also, for all you know, people are skimming over your thread because they can't try the download, even though the story is interesting. I mean, that's how I started. I saw the plot and screenshots and decided, "I'll try this."