I understand your points and I think there is a chance of this going wrong. Especially with the current incentive structure behind it. I personally hate smartphones because the incentive there is to get people's attention and sell it.

But without this incentives I could imagine a future where Smartphones where actually good and have a more positive impact.

But back to culture. I don't see the problem of people listening to their own created music. Even now a lot of people make e.g great photos just for them selves. As long as we don't force people to do so that's fine in my books.

Still if the incentives are bad, this can go very go wrong in very distopian ways.