I can't figure out whether this is the Apple TV or the Samsung.
The Apple TV box feeds to the TV, so the TV has no influence over the behavior on the box in this regard.
As your screenshot shows that you are in the (Apple) TV app on the Apple TV box, the YouTube app wouldn’t be visible there, but at a level higher (go Back/Menu a few more times), on the Home Screen (which is different from the Home tab in the TV app).
You may also configure the TV button on the remote to go to the Home Screen, instead of going to the TV app (for single-click, not click-and-hold which is for Control Center, not double-click which is for the App Switcher).
When I hit "home" I get a spinning circle and nothing happens (picture below).
The spinner indicates waiting for something. It seems to be trying to fetch content, but is not getting a response from the remote server in a timely manner.
Possibly the internet connection isn’t fully functional.
Try restarting the Apple TV box, the router, and optionally any other network gear in use (switches, mesh nodes, repeaters, etc.).
Try force-quitting the TV app, then launching this app again.