One major upside of newer languages like rust is that they can start out with these "newer" primitives, with a standard library designed around them and without

One major upside of newer languages like rust is that they can start out with these "newer" primitives, with a standard library designed around them and without tons of "legacy primitives" that do the same thing, but worse (like how python has 4+ distinct ways to print a string with variables in it, all in various degrees of popular use). Once your language has aged a little it's hard to impossible to take old primitives away, but you still want to adopt ergonomic improvements in order to not be left behind. Until at some point you become a language nobody can master in its entirety.