Not sure if this helps the discussion at all, but I got a hand-me-down 3rd gen Apple TV about a year ago and I think it’s great. 1080p Netflix and Prime playback work wonderfully, the UI is simple and responsive, and (after some hefty wrestling with macOS wake-on-LAN settings) it plays back TV shows and movies from our old Mac Mini server to fill any streaming service content gaps.
If you’re a tech nerd, you might remember that the 3rd Gen Apple TV runs an A5 CPU, originally used in the iPhone 4S and iPad 2 (it’s actually worse, since the aTV’s A5 is only single-core). Given that a 3rd gen model with a 10-year-old chip is still extremely usable for non-4K/non-HDR use (and still receives software updates) it’s probably a device people don’t upgrade all that often. As such, I’m guessing it doesn’t move a huge amount of yearly units, but I certainly hope it sells enough for Apple to keep making it. I’ll have to upgrade eventually!