It is true that there are complexities in pop music, especially in the modern age of "featuring" artists, but:
1. There are complexities and complexities, and classical music involves the latter.
2. If anything, much pop music seems designed to hide things like composers and session musicians as often as not. The fear seems to be that if people realized how few pop artists write their own music, they'd think less of them. I'm not sure I agree, but the point is that improved metadata is not what everybody involved in pop is looking for. Since the metadata would need be supplied by the labels, I don't think the uptake would be as high as one might hope.
The best example of non-classical music that might rise to a similar level of complexity and care is touring bands like Phish or the Grateful Dead, if all of their live recordings were available officially.
That sounds like a schema to me. Hell, even popular music can have such complexities, it’s just that they’re usually ignored e.g. e.g. if you want to correctly tag a cover featuring a rapper, that’s basically a performer (cover band), composer (the original band, or the actual composer as that’s often not the band), the soloist (the guest), there’s also the backing band and vocals which may have their own identity, and the venue may or may need a mention (e.g. a tiny desk live usually has a different feel than a concert live).