You're still obliged, in law, to deliver what you promised you would.
No, you are absolutely not in this case. Kickstarter is microfunding investments in a project/company, not a purchase of a product with a specific guarantee or warranty. The fine print says as much. Sure, if they absconded with your money for a vacation you could try to sue them. But in this case they tried in good faith to deliver what they could and ran out of cash before implementing all features (not only common but almost universal in the games industry - if you haven't seen this a dozen times you are not a gamer).
t's not easy, but it's no different to any other payment.
This is ABSOLUTELY incorrect. It's not a payment at all, you are NOT buying a product. You are investing in one, and you get a reward if it succeeds. Luckily the majority do, but if they declare bankruptcy and don't product anything because of mismanagement or just bad luck, you get to line up as an investor to collect/sue for any capital invested, which means you are 99.9% shit outta luck.
"Just X amount of money more and you could see how it plays!"
Welcome to the world of "venture capital." Just luckily for the investors it's $50 at a time and not $50M.