Ha ha not true at all. I care more for audio than video and fire stick does give out great sound. If your receiver is showing DD+ that means it is getting multi channel audio. Try playing with the surround speaker levels. Are they absolutely silent during movie playback.
Yes, i tried with my friend's.. called amazon multiple times and they got a log from me by activating developer mode but nothing happened..
so i switched to shield
yes i took note of all the settings and did a factory reset too and more over if there is a issue with my receiver why it is happening in onkyo and denon too strange