As they said in their public patreon post and if you tick their show more menu on the main description there is a link to their roadmap. This has been asked so many times we might actually need to put this on the main post. The demo's are just glorified sex builds until the vertical slice.
It's a porn game first and everything else second. They wouldn't be getting anywhere near the funding they need to sustain a 16ish person team if it wasn't for these demo's giving what the majority of their supports want (which is sex in an adult game).
Hopefully the vertical slice will give us a good demo on what to expect. I'm not expecting a ton of content from it obviously, but I suspect it should be enough to give us a decent view of all the work being done while they whip up sex demo's every other month.