It is a sign that the Mozilla insistence on VS is harming the project. clang/gcc are also available on windows. They would really help to unify/simplify build system and the development process. Another serious weakness is the lack of ability to build FF with gtk on windows if I so desire. Moreover gcc offers windows 64 bit options. They should also support a modular codebase with complete third party dependencies. But more importantly it seems that they hope Rust cab become the de facto way of developing FF. It is a promising direction but it cannot remedy the VS mania.