Yes, Amazon Prime is there now on AppleTV. At one point it wasn’t. And then for a long time it was impossible to purchase content on Amazon Prime in the AppleTV app. Minor irritations but irritations nonetheless.
Here’s another good example. YouTube is not available on iOS or AppleTV in 4K. Very irritating. YouTube is available in 4K on Roku. Spotify is not avaiilable at all on AppleTV (in fairness, Spotify is normal quality audio, which I can’t abide on Roku but it doesn’t bother my wife who uses it).
Roku plays much better with others than Apple as Roku is not passive aggressively trying to firewall its own services.