Comment by badsectoracula

The reasoning does sound serious: "The properties of the language are not yet well-understood, having selected an unusual language design point (e.g., borrow checker) and having existed only for a relatively short period of time". It isn't just "it isn't popular thus it is not good" but "it does something weird that no other language does and because few people use it, we haven't yet figured out what potential issues that weird part may have".