Once Google TV Launcher is disabled, Shield picks the next installed Launcher on your system as the default TV Launcher. Be aware that most 3rd party TV launchers aren't very configurable or polished but will launch your other apps. Maybe try a few different ones before disabling Google TV Launcher.
Works fine, but it is not the most stable software. Plenty of add-ons and themes, and (probably the reason why it's popular) you can sideload some pirate TV add-ons.
It has been a while though, so I might be outdated on this, but I'm guessing it's still not possible to log into spotify from it, browse the spotify library / your playlists, use device remote play from your phone to the tv, and so on. Same goes for youtube (though I do remember some useful-ish youtube plugins, they didn't go beyond logged-out browsing)
None of them perfect, but you can roll back to what you had before.
I'm frankly not sure opting into Apple is a solution to the problem at large. It might be a temporary fix, but at the end of the day you're still using a proprietary system which might decide that ads are lucrative tomorrow.
There's no such launcher on Windows that doesn't deal with the pitfalls of it being Windows. Even something like Steam's Big Picture doesn't really work very well in certain circumstances because you can be thrown out of the launcher onto the desktop unexpectedly by games it launches.
I think the only way we could see a good implementation of this is if Microsoft themselves made it. They tried doing something like this with Windows Media Center but I think that they're better positioned to try again now that streaming services are ubiquitous.
I personally just run mpv on my Linux box plugged into my TV and connected to a DLNA media server in my home and use my Android phone as a remote with KDEConnect, I'm not a big app person. I mostly watch YouTube videos my media server auto downloads when they are available from creators I like. For my family I have Netflix.
You're right it's not as nice as using a TV remote though! I bet Kodi or Plex, etc. would be more navigable with a remote. I wonder if you can get a Bluetooth remote that connects to a PC...
I kinda imagine that a "real solution" would involve some kind of Android environment, though. Your solution works, if the user has not opted into the youtube/spotify/netflix ecosystem. If they have, it's not a real solution.
I care about my youtube account -- I pay for it, in fact. The recommendation engine is extremely good if you curate it, and I've curated it a ton. YouTube is a beast for knowledge/learning center. Spotify has a really good and extensive music library which makes "not pirating" a real option.
At the end of the day, you need a good UI that implements the features of those services. No third party is working full-time to implement these in open source, and they'd likely shut down if they did. So relying on the upstream apps somehow makes sense.
Let's say I want to opt out of Google for this. What the hell do I do? I do have a Windows PC attached to the TV, for gaming, but if I wanted to run the apps above they wouldn't be optimized for TV input, they'd be cumbersome to use. Attaching a Linux box isn't going to work particularly well for gaming either.
Seriously, what are the alternatives there?