This article is poorly titled; it's about the lack of namespaces on crates.io. Rust does have namespaces. Cargo is capable of supporting registries that use namespaces. Using Rust doesn't even require one to use Cargo, and using Cargo doesn't require one to use crates.io.

(For the record, I do think that namespaces on crates.io would be a marginal improvement, but the benefits are often overstated and it would add organizational costs that the crates.io maintainers can't currently bear. The amount of ire over this topic is disproportionate to its impact.)