And yet, people are going to use async in Rust. The feature has already proven itself useful long ago in other languages, beyond the timespan a fad could survive. Everyone started out doing it the other way and got sick of it.
On the voodoo ridden land that is software development, we have plenty of clearly harmful fads that are much older than Rust and yet practiced everywhere.
Up to now, rust async has lasted for less time than the NoSQL craziness. I'm hard pressed to think of any large fad that lasted less than it.
Async is much older in other languages. It's new in Rust, and time will tell, but I don't see it playing out differently this time.
Btw, the turnaround time is longer with a database, which often forms the foundation of a system. NoSQL bandwagoning was so destructive in part because of how long it looked like a good idea each time. Same with ORMs.