Kickstarter backers donated. They are not shareholders and they shouldn’t expect to be. Expecting a return upon acquisition is as preposterous as expecting a dividend next time you buy an iPhone.
As long as you received your reward, you can’t complain. Kickstarter is weird because people feel like they are investors; the ‘backers’ terminology certainly doesn’t help. There are sites that let you crowd-invest (like Seedr), but Kickstarter isn’t one of them. It’s something people have to just get used to.