Unfortunately, picture quality these days has as much to do with the HDMI spec and capabilities of every device in the chain as it does with a quality TV. The weakest link is often times an aging cable box more than an aging quality TV. There are still low power channels broadcasting in 480i to this very day. My in-laws wasted good money on a TV because they insist on watching the standard definition channels and stretching them rather than tune to the HD. Sometimes, settings in the device and AVR can improve picture quality without touching the TV. There will be issues between some HDMI 1.4 and some HDMI 2.0 devices. While not quite finalized in implementation, HDMI 2.1 isn’t looking too hot either. F#%kin’ HDCP! Sorry, it’s a tick.

I hope you can fine tune it all. Don’t give up!