C++ needs its runtime for a lot more than RTTI. My understanding of C++ is that its so limited without its runtime as to be nearly useless. Rust seems to retain much of its character still, and certainly has enough expressivity to bootstrap its full self.
Frankly it doesn't sound much different then C++ making RTTI optional.
Rust is a classic example of what happens when you try to anticipate everything that could ever go wrong, and then build a language feature that tries to make that less dangerous."There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies." - CAR Hoare.
How recently have you looked at it? I certainly respect your opinions on programming languages, but I'm curious as they've really cleaned up a lot of the cumbersome syntactic patters that had appeared. The language has become markedly clearer in the past 6 months or so.