Well, we’ve been through this before: XML-RPC vs. REST+JSON. And no one remembers SOAP—which had tremendous backing, but was just so riddled with tags, you would just get lost in the stack.
ActivityPub is just unbelievable—so many layers of JSON-LD, Webfinger, Salmon.
Webmentions seem so much simpler—even though they’re not exactly comparable. However, Microformats are very difficult. They just are messy in practice—don’t you think? I kind of wish we could go with a combination of Webmentions and JSON Feed. But it’s too late to go inventing another spec.