I think your comment hits the bullseye better than many others I've seen around this. It very much looks like the language stopped progressing with async.

Seems like they just tried to be everything at once, and reached some sort of a critical mass. It probably didn't help how Mozilla dropped lots of their Rust projects and staff at roughly the same time.

It's still a very good C++ replacement. I think its role as a higher level application language is more of an open question.