No, it's a valid complaint: Rust shouldn't require MinGW. The biggest problem here is that Rust doesn't include its own linker, and the moment it cannot use link.exe.
It may be a valid complaint in the sense that not supporting MIPS is a valid complaint. Rust, because of the decisions made in its design, is going to attract developers of low level systems, server-client architectures, etc. If you are developing the type of systems that Rust excels at, wouldn't you also be the type of developer that has no problem developing on and targeting Linux, BSD, MacOS, etc? Or am I missing something? Obviously Servo would be a good use-case, but apart from browsers, nobody targets Windows native software anymore.