I'll say up front that I'm a non-audiophile, and so I'm offering my opinion from that point of view.
I find the Spatial Audio / Dolby Atmos thing weird for a number of reasons.
First, the dual branding seems clunky. "First I listened to music in mono. Then I listened to music in stereo. Then I listened to music in ____" I'd be willing to bet that even amongst people who care a lot about this stuff you'd have a hard time getting consensus about how to fill in the blank.
Second, the fact that there's a brand name attached to it at all feels wrong. One of the great things about music is its accessibility to artists as a medium: lots of great music will come from young folk in their bedrooms with cheap recording rigs. Will they pay a license fee to Dolby? There are many examples of great art that's wrapped up in proprietary technology (video games, for example) but music feels so basic to the human experience that (a) I don't want a brand name attached to it, and (b) it'll never become standard because people are always going to make recorded music without engaging Dolby. An historic example that comes to mind is Technicolor, which feels like something from the olden days. Groundbreaking in its time but no longer culturally relevant.
Third, it does indeed seem weird that this technology would be implemented by a middleman. Sometimes I'll fall in love with a song that has a lot of nuance (like a Bjork song, for example), and I'll tell someone about it, and they'll pull it up on their phone and hold the phone next to their ear, and I'll say, "well, you have to listen to it in headphones." Now I'll say, "well, you have to listen to it in headphones. Actually, this specific make and model of headphones. And also through an Apple Music subscription." (I realize I'm being hyperbolic here, but I think there's a valid point to be made about shared experience where music is concerned.)
And while I’m a fierce advocate of the idea that it’s okay for people bring their own interpretation and meaning to art – I don’t believe the artist should or can have total control over how the art is consumed – the mass remixing of all this music feels more akin to the remixing of the original Star Wars movies than it does to the restoration of a painting.
Finally, I just don’t think very many people will care. I would be willing to bet that a minority of people could pick out a Dolby Atmos song from the original, and of those that could, it seems unclear they would prefer the Atmos version. There are a hundred things I would have chosen to improve about my Apple Music listening experience before sound quality: making the navigation of the music app make any sense whatsoever, and having the AI generated “stations” not be terrible, are two examples. And I know, I know, it’s different groups of people working on different things and it’s not like they can reassign a sound engineer to rewrite the UX of the music app, but it feels like if there was a water leak above my desk in the office and the office manager’s solution was to buy me a nicer chair.