Compilation times were a consideration, but they were a subservient consideration to the prime considerations of 1) being as memory-safe as GC'd languages, 2) exploring the limits of statically-guaranteed thread safety, and 3) being as fast and memory-efficient as C and C++. If Rust had been willing to compromise on those goals and instead had just, for example, used a virtual machine with pervasive garbage collection and been designed for dynamically-dispatched generics then you'd get a lot of compilation time reductions for free, but the world didn't need another Java, it needed a more secure systems language to stand up against C++ where every previous challenger had failed.
replyNo, Rust is not at the paretto frontier for your mentioned 1, 2, 3 and also 4 compilation speed. It could have all of those things and also just have faster compilation. Rust devs have talked about how they have some regrets about not optimizing more for compilation, but instead another attribute got optimized in terms of paretto efficiency - the language's development time. Arguably I think that is the single worst trait you can optimize for in language development, because by saving a little time developing the language you cost humanity, let's say hundreds of millions of hours of development time downstream from you, with millions of users being less productive.
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