> why is it immature for Rust to ship a toolchain and package manager through a sidechannel, but not Haskell?
Haskell also feels less mature to me than C, with fewer POSIX functions being readily available, but as mentioned above, with Haskell (in my experience; the experiences indeed seem to differ) it is "one or two dependencies have to be pulled from Hackage across multiple projects and system versions", while in Rust it is rather "I failed to pull common logging and argument parsing dependencies on a single up-to-date stable system, and apparently one is supposed to install and update its compiler, package manager, and libraries separately from the rest of the system". Though some use ghcup or Stack, which also aim working without a system package manager, but at least a system package manager is a viable option.