Additionally, not just up next, but based on my subscription patterns, content from CBS, Showtime, Starz, AMC+, Epix, HBO, Cinemax, Sundance, Acorn, BritBox, IFC Films, and MUBI, as well as Apple’s TV+ channel, are all browsable without leaving the consolidated TV UI, and do not need an app installed at all.
From your list, Hulu, Disney+, Netflix, and Prime all do need apps installed. I do have to go into these to discover their own algorithmically proposed (personalized) thumbnails. But for day to day watching, the only app needed for each brand you happened to mention (except Netflix) is the TV app, and when searching for a show, shows from all of these (except Netflix) are in the search results.
Unfortunately, there are apps that work on Apple TV that do not play nice with the consolidated view and watch-roll. Some that were well integrated, backed off, most likely having to do with the waterline on viewer measurement / analytics data.
Netflix is the prime offender here. It wasn’t integrated, then it was, then it wasn’t again. They seem to have landed on a (for them) happy medium, where if you have Netflix in your home (top) row of icons on Apple TV’s home screen, “mousing over” (aka selecting w/ remote) the Netflix icon does show you your Continue Watching and Trending Now options, so you can go directly to those without opening the Netflix app itself. But they no longer show up in even the search interface, which probably keeps me subscribing to and watching other sources more than I need to.
To help give a signal to media owners, and to Apple, I systematically un-subscribed through individual apps and subscribed through the fully integrated “Channels” as those channels appeared. This individual statement is lost in statistical noise, sure. But what you describe is clearly better for the home user, and if enough folks do it, they’ll catch on.
On my Apple TV I can search for shows on HBO, Amazon, ESPN, etc. All of my recently watched shows, regardless of streaming service/channel, show up on the main "TV" page. I can use Siri to search across all services, e.g. if I ask Siri to play The Office it will find it on Peacock and play it directly from there.
The large exception here is Netflix, apparently they don't hook in to the Apple TV API like the rest of these apps do (I imagine it's the same on the Google TV).