90% of us watch Netflix, Plex, YT TV or some other streaming service, how do I watch these with 4k quality without connecting to the Internet? That's just an unrealistic request for 90% of TV users.
Use a separate, not ad-riddled device plugged in via HDMI. If you have a game console it can do this.
I don't know what's good for Android TV boxes it used to be the NVIDIA Shield was a well regarded streaming device but it's really old now. Google makes one (Google TV Streamer) and you can install a custom launcher if you're a bit technical and the "suggested content" of the stock launcher bothers you. Same for other Android TV boxes.
Apple, like them or not, makes a really decent TV box with no system level ads and an interface that mostly stays out of the way.
I run projectivity on my shield. I definitely have told people to buy them. There is a reason they still often resell around their original 2019 market price - they've maintened their value. For large screen or projectors the proprietary 1080 to 4k upscaling is still unmatched imo. I don't use mine for gaming, but many gamers still like them for their gaming capabilities as well. If you buy one and don't like it there's still a good chance many months later that you can resell at or above what you paid for it too.
If you have some technical knowhow, you can configure your router to let things like Netflix through, but not the rest of the OS. Or you can try your luck with PiHole or similar.