First - apologies if this is not the right forum to raise this. I raised a bug report on the async-std github repo back in May but got no response.
According to the README in the async-std repo, async-std has been discontinued, however this message is not visible on the docs.rs landing page or on the async.rs page (which is linked as the homepage on docs.rs).
Given the name of this package & the slick home page it is likely that people stumbling on one of the above two resources will think async-std is a semi-official crate and a good choice for a new project.
I don't think the deprecation of async-std was all that widely publicized - after stumbling on the README I did manage to find a reddit post but not much else.
I'm hoping someone who has commit authority on that repo and/or the async.rs website sees this and can make the deprecation more prominent.
I've uploaded a 1.13.2 release with the sole change of adding the deprecation notice to the documentation, so it shows up in another place on docs.rs. (It already showed up in the crate description on docs.rs, but if you go directly to the library documentation that might not have been visible, so now it's right at the top of the library documentation.)
We didn't add a deprecation warning for the exact reason you mentioned: it'd be excessively noisy.
I'll check in with folks familiar with the async.rs tooling about updating that. We've talked about making it a more general async resource, and documenting various aspects of async in Rust. That's a larger task, though, and perhaps we should start with just ensuring there's a deprecation notice there.
Good idea to transition the async.rs site to a more general rust async resource, if possible.
It's a bit of a gap that there does not seem to be a good way to flag a crate as deprecated. It would be ideal to recieve a single warning when compiling code that depends on a deprecated crate. Our CI system would then have alerted me if that were the case.