Spotify is a good example of something that could work identically to what it does today self-hosted. No change anywhere, no extra setup at all, except for the fact that storing the entire spotify library is impractical.
When I talked about a more user-friendly device I meant something of a smart-home controller. Not a general purpose script that glues together some open source packages that each require a weekend of setup from an enthusiast... No, that none of those has taken off doesn't surprise me the least (that doesn't mean they are useful or that I could see myself using one, but it is not for average Joe).