A successor to bandcamp would be really nice. I think it is hard to determine if a site will become one, because it is largely about network effect—Bandcamp had enough users (customers and artists) that it was, like, worthwhile to give them your credit card info… Totally tangential and probably revealing that I have absolutely no understanding of the music creation ecosystem and process, but is there room for, like,…
Bandcamp didn't even accept people's credit card info (maybe it's changed in recent years and they have more payment options now). They outsourced payment processing to PayPal.
Most small shopping sites in USA don't handle their own payments due to regulations.