I also have the impression that "everyone" buys an apple tv/Chromecast/etc anyways because of limitations in the smart tv or just ease of use. It makes a lot of sense to have these things separated except for TV manufacturers that want you to buy a TV more frequently.
Can we produce substantially inexpensive black-boxed hardware that they desperately want in order to cut costs, but interferes in dissatisfying but barely tolerable ways with the quality of life too? Can we occasionally make it send messages in-store to their customers that the execs wouldn't want or approve of but find themselves putting up with because it's relatively benign compared to a worse bottom line?
Using a computer monitor or specialist/signage TV is both expensive and offers a worse experience.
My Samsung TV has never been connected to the internet - we use a Roku box to feed streaming content to it - but it's still laggy and unresponsive by default, getting worse over the course of a few months until we decide to factory reset it again.
At one point it was so bad that I pressed the "change source" button a couple times, noticed it wasn't working, pressed the volume buttons, then the menu button, assumed the remote was dead, went to find some batteries in a drawer, took the remote batteries out, and then the TV rapidly switched sources, changed volume and opened the menu over the course of half a second.
But I expect that of my car infotainment, my computer monitor, and a recently purchased signage screen as well. Finding a device (any device) that didn't behave like this would me more shocking. I tend to think that the best thing to do is buy the most popular product, from a known brand. Because at least then there are millions of people having the same experience, increasing the chance of a fix.
We get amazing hardware in many cases these days. The quality of the screens in TV's these days is completely unbelievable. And you can get a decent one for a few hundred. I too wish there was a brand that would spend a little more on better UX (both hardware and software). But the harsh reality is that it doesn't sell. Rumor doesn't spread that BrandX has snappy intuitive menus, fewer bugs or less ads. The commercial says that UsualBrand has new magical colors and ultra high def thingamajigs, and that sells TVs.
The ARM chip in the AppleTV is anything but slow and the only thing I had to do to prevent ads on the Home Screen is to remove Apple’s apps from the top bar and replace them with my most used apps.
And often by that point they’re looking for an excuse to buy the new shiny anyway.