Netflix playback issues on AppleTV

[Socko]

I've googled this and I'm not the only one, but I didn't find any solutions yet, so maybe someone on here shares the same frustrations as me.

I've an old 1080p projector which does the job until I upgrade to a 4k projector.

On my AppleTV the video quality of movies and tv shows is not good.
It's blocky and the resolution almost looks like 720p if not even lower.
The audio is top notch. On my receiver I get Atmos (when available) and it sounds good.
My AppleTV is connected with an ethernet cable, so the wifi is not used.

As a bonus:
When I start the Netflix on my Sony UBP-X700 blu-ray player the image is nice and sharp, but the audio seems to go down to maybe 5.1 with hardly any rear speaker activity. Definitely no Atmos anymore.

So it's either good quality sound or good video

Anyway, does anyone know what's going on? Other streaming services like AppleTV+, Amazon Prime or HBO Max all have good quality video on the AppleTV device. It's only Netflix that sucks.