Hello @Nettuno,
I think it is unfair to complain about things that Volumio has never advertised as being capable of…
For Amazon Music HD, the problem lies with Amazon, not Volumio, for not releasing an API that would allow developers to write a plugin for it. There are only a handful of devices with Amazon Music integration: Bluesound, Sonos, some Denon AVRs… that’s about it. They all have specific arrangements with Amazon that have allowed them to integrate Amazon Music into their products which, by the way, run on their own proprietary systems. Volumio is an open-source project (well, mostly open-source) that can be installed on a wide range of hardware. For now at least, Amazon Music doesn’t seem to think it worthwhile to open up its API to these kinds of project.
As for the YouTube plugin not being able to play videos… well, Volumio is an audio player from day one. A plugin will not automagically add video-playing capability to an audio player LOL. If you want to play videos, get a media player like Kodi / LibreELEC. By the way, the YouTube plugin is not an official plugin by Volumio, but written by me to provide another source of audio for its users (and I am not part of the Volumio team).
Now, I would have to agree with you about Volumio playlists / favorites. The implemention leaves a lot to be desired, and there are many things in Volumio that can be improved or fixed.
The point is, if there is something that was advertised but is in fact broken or missing, then it’s absolutely fair to complain (whether it’s a paid feature or not). For things that are missing but simply on your wishlist, then raise them in the forums or, if others have already mentioned them, express your interest in those threads. This will at least get the devs’ attention, although I would rather see them spend more effort in sorting out the existing issues or provide more help to users in the forums.
Just my 2 cents.
-Patrick