Hey thanks for the post
I'm one of the makers of the game, ductape you make a valid point indeed, we're using the pre-order / donation system purely because we came off the back of another game (Privates for Channel 4) but since that had a development budget, and no subsequent funds from sales since it was a free to download educational game, we found ourselves in dire straits moneywise once that had finished, and so we had to announce our secret project way early and appeal to people's better nature to help keep us going and keep us working indie full time.
And when we released the vid we did on the proviso that we felt we had to due to some people were weary of giving money based on a few screenshots, and some even making quite brutally accusations of us making screen mockups and setting up a fake site to scam people. It felt we needed to show something, and this is way earlier than our planned video release. We plan on releasing a more comprehensive trailer in a couple of weeks, but we're not quite there yet and combat is the only thing that feels complete enough to demo in video without too much placeholder art and other things. There is more to it than in the video, already, and we've got 30 years of commercial game experience in the team, so we at the very least are perfectly confident in delivering.
But yeah, we understand your point of view entirely, and are fully aware that we're perhaps asking a little much at this time, so obviously it's up to the individual whether the investment feels worth it.