> But seeing the pace of new features introduced into Rust, I'm a bit worried that some of the older features will soon be declared "non-best practice" and turn into C++-style cruft.

Is it just because you see additions of new features in general or there are some specific issues? For me new features do not make 'bad practice' from old ways. As example in older versions you had to be more explicit with lifetimes, but that is just convenience.