Been a user for the last 7-8 years and I love the UX.
There are no app suggestions or notifications on Apple TV (or at least I turned them off about 8 years ago).
I have been happily streaming media off my computer with Apple TV and have never had a single issue with it.
Even then though, I'm an on-again/off-again Plus subscriber so I don't even mind it because it often times suggests shows that I might want to subscribe for.
I'm not sure how many Apple TV devices they sell, but I've always viewed it as super underrated, just a clean piece of hardware with great "It Always Works" functionality.
Even then I don't quite consider it quite ad-free. Content I've purchased in iTunes Movies or iTunes TV Shows will always show the store on launch or will switch to the store if you pause content for some amount of time.
Otherwise, there aren’t really any ads except that if you linger over their app icon, it has a kind of “now showing” effect (no sound though). Seems a little more privileged compared to other apps in how much of the Home Screen it can use, but it’s really not obtrusive.
I really like my Apple TV.