I thought the author's point was relatively clear: Rust might not be a good fit for the kind of tasks that need more concurrency than raw threads can give you. Such programs should be written in some other language instead.
> Maybe Rust isn’t a good tool for massively concurrent, userspace software. We can save it for the 99% of our projects that don’t have to be.
Anything that waits on I/O needs concurrency (but not necessarily threads). Web backends, web frontends, deeper backends, desktop GUIs, that's probably 90% of software right there.
I interpreted the 99% thing as referring to all software. If it's just Rust projects then sure, then again anyone who needs async has probably been avoiding a language that lacked async until recently.
> Maybe Rust isn’t a good tool for massively concurrent, userspace software. We can save it for the 99% of our projects that don’t have to be.