> If they want to retain or grow their paying subscribers Apple needs to improve their software with the same attention to quality they devote to hardware.
I get your point, but no, they just need to sell more devices; act anti-competitive by bundling Apple Music on every iPhone's homescreen, thus giving Apple Music billions in free advertisement that Spotify could never get even if they paid, and by setting Apple Music as the default. Then, make it hard to switch (e.g. if you cancel Apple Music, you lose your library 90 days later). Make sure Apple Music has the home advantage by sharing advance knowledge of new APIs and hardware with the Apple Music team, but obviously not with Spotify.
Plus Apple has strong psychological advantages, since Apple users seem more likely to blindly want to stick to all-Apple solutions and default apps regardless of app quality. Compare that to Windows, where users can't wait to get rid of Edge, and Android, where only a minuscule portion of people insist on an all-Google experience.
I don't believe there's any real "corrective mechanism" inside Apple to make Apple Music or TV+ the very best, because they don't need to be.