Can't skip ahead to sections of their content you want to view and instead are forced to watch it in sequence.

Either that or can't skip ads, ala legal dvd playback

I'm still not seeing the part where this is Roku's fault at all. It's Amazon's app responding to the controls the way Amazon wants it.

There's no platform with a standardized "fast forward" experience - Apple TV, Google TV, Fire Sticks, whatever are apps running on a device and those apps all implement their own navigation controls.