I wouldn't beat yourself up about lack of interest after a demo which lasts 5mins!
It's a fantastic demo and sets a great starter.
Like you said you've already done final play testing on the next stage which sounds like its starting to flesh out options and see more.
Take a look at similar games like
Alpha Omega,
STWA: Unbroken here on the site and how successful that has been. I say similar - STWA you have a male MC and create a Harem but what I'm getting at is that the
fighting/wrestling theme is very popular.
Keep your head up a lot of these other games launched with much longer demos etc. to give people a taste. Also remember some devs here don't update games for 3-6 months lol, so people won't mind if its a while until you bring something new. One of my favourite games gets 2x updates a year but there's loads of content each time.