Activity Pub is much more flexible, the tradeoff being that it’s more complex. ActivityPub is basically a flexible CRUD API specifically designed for social networking, with support for federation.
You could fulfill the purpose of RSS with ActivityPub. But, it doesn’t supercede RSS/atom, because the simplicity is valuable for the cases those protocols handle.
Activity Pub is much more flexible, the tradeoff being that it’s more complex. ActivityPub is basically a flexible CRUD API specifically designed for social networking, with support for federation.
You could fulfill the purpose of RSS with ActivityPub. But, it doesn’t supercede RSS/atom, because the simplicity is valuable for the cases those protocols handle.