My main complaint is that there isn’t a consistent experience between apps. Things are in different places, actions do different things in different apps, no gesture support, subpar players with horrible scrubbing, etc.
I think all apps should be held to a few basic UI/UX standards so going from one app to another isn’t a completely different experience.
The attached photo is just one example. Within the Apple TV app itself, long pressing an icon brings up this great menu allowing you to go straight to the show or the episode page. Long pressing in most other apps removes the show from your now playing list! All of these conflicting actions need to be rectified.
The apps you've mentioned are simple web wrappers that display HTML5 content. If you go to youtube.com/tv you'll get the exact same web page that these streaming apps display. They do this because it's cheaper to maintain and you get the the exact same experience on every device. Not playing the devil's advocate here, just explaining why these apps are so bad and why I don't think this is going to change. In fact, Google did provide native apps on some plattforms and later replaced them with their low-quality HTML5 apps.