Question

, in almost every modern tv since last 5/6 years at least you get apps for pretty much everything and also they support Dolby Atmos and HDR.
What is the major use case for a device like Apple TV?
I do have a couple of them but have left them unplugged as I’ve found them to be unwanted in the household.
That "getting apps for pretty much everything" doesn't seem to be true at all... unless everything is defined as only the major streaming video apps plus what is typically a handful of some others. That would be like saying since Macs have apps for pretty much everything one can do on iPhone or iPad, what's the point of iPhone or iPad?
There is a relatively enormous App Store for AppleTV vs. any of the TV app stores. And apps for AppleTV are usually kept functional until an AppleTV generation reaches that "long in tooth" state via tvOS obsoletion and/or Apples "buy again" game of vintaging stuff (that can still work just fine).
However, even if some TV brand covers both of those bases as well (do any of them???), AppleTV is fully compatible with all Apple ecosystem benefits while TV apps are not. So if you are deep into Apple, you'll find that you can generally do more with AppleTV than you can with TV apps.
If app uses are mainly limited to major video streamers (Netflix, Disney +, etc), TV apps can be just as good. And note AppleTV the app is very far from offering the functionality of AppleTV the box. Some seem to perceive the app being available on TVs means there's little-to-nothing more the box can do. That's completely untrue.
Most simply: all it takes is as little as ONE app available for AppleTV that is NOT available for TV. If there is ONE+ app(s) that people like on AppleTV that they can't get on the TV, it may be able to justify an AppleTV all by itself. For me, that would be the Computers app that comes stock with AppleTV. Often overlooked, it is a
very functional app that takes advantage of content I
own (vs. content that can be rented or purchased). It's not about selling me something but about serving up a wide variety of media I already have, be that movies, tv shows, home movie collection, photos, music collection, podcasts, etc. Subscription cost to use it for all of that: $0. Rental costs for content available within it: $0. Cloud subscription for access any of that: $0 (no cloud required).