In my case i've got a flagship panel, the Samsung Q90R (which cost me about $2500) which has a quad core Qualcomm chip with almost instant responsiveness. My Apple TV now sits in a drawer. From the reviews i've seen all the flagship brands like the LG, Sony are all super fast and quite good. I suppose for people buying entry level panels they aren't going to be springing an extra $200 on an Apple TV so they'll put up with a slower experience because it comes included - and that's what consumers appear to be doing.

Was this a LG C9 OLED tv? Just curious in how much better and in what way is the Apple TV to the native app. I haven't had any issues afaik. But I haven't used the Apple TV 4k before either, so I guess I wouldn't know if I'm experiencing subpar quality.

It's at home and I'm at work so I can't look at it right now, but it's one of their newer 4K UHD TVs with webOS. I tried it on the guest wifi for a couple of days to see what it would be like, and while it wasn't bad (like I couldn't look you in the eye and say "this sucks, don't use it!"), it just wasn't as good as an external video source. There's no reason it couldn't have a perfectly fine hardware video decoder that's as nice as one you'd find in an external player. Still, its SoC and other support hardware just isn't going to be as nice as what you'd find in a dedicated box. Maybe the network stack isn't as optimized because the CPU has to handle a lot of stuff in software. Or maybe its OS's memory allocator isn't as quick. Or insert a thousand other things that might make a TV's dirt-cheap-as-possible SoC handle all the housekeeping around keeping the decoder fed with data as efficient and smooth as possible.

And as others have pointed out, you're pretty much stuck with what it ships with. If my Apple TV breaks or gets old and unsupported, I can trivially switch to a Roku. If the SoC in my TV gets old and unsupported, there isn't jack I can reasonably do about it other than throw out the whole TV and get a new one.