The beta is for backers at the $80 tier or higher. Did you qualify for that?
And this might be a good place to remind people that starting with Mega Man 2, the robot masters were based off character design submissions from Japanese schoolchildren. Those games turned out pretty damn well, IMO.
The kind of input that backers have so far have come in the form of surveys over small details, color schemes, etc. Nothing major. The men and women at Inti Creates know what they're doing.