You shouldn't have to "load up" the app, it shouldn't be a thing that tinkerers sideload. It should be in the store.
Why can't my Android TV from another brand download it? They're doing it wrong.
Because the TV have app stores just like iOS and Android.
And the TV vendor wants to be paid.
You do understand that smart tv apps collect and sell user data, right? They use that data for ad targeting. And they get paid for the apps they carry just like phones and consoles.
So you can download the XBOX android phone app but good look sideloading it if the TV manufacturer doesn't want it there.
It is not up to Microsoft.
The TV manufacturer is in control.
Just like Apple and Google on the phones.
MS did look into doing their own streaming device to plug into any TV but the cost and complexity to build, sell, and operate it was more trouble than just paying Samsung, Amazon, and LG to put the app on the TV/streamer store. More deals will follow. Just don't ever expect the app on Sony TVs or Apple streamers. No amount of money will get it there.