> But the rate at which it is growing and changing means it won't actually take 30 years to become the new C++.
I very, truly, seriously doubt this is true. First of all, as I said elsewhere in the thread, Rust has been changing very slowly lately. But beyond that, a significant reason for C++'s complexity is that it's sort of two, possibly three different languages: Modern C++ is very different than C with Classes. It is a miracle that they retrofitted a new language on top of an old one, but there's no indication that Rust will ever do that. The quantity of change is one thing, but the qualitative aspects matter here too, and I feel like you're only considering the quantitative aspect (which, I also disagree with, to be clear.)
Auto is the only one I can think of.
(I am just curious, I have no idea how common your parent's comment is in real life.)
I have it straight from the horse's (Bjarne's) mouth that there will be no more editions of "The C++ Programming Language" because the language is too big and writing a book too time consuming to actually cover the language as it currently exists and what it is going to become. It's own creator admits that the language is too big to document in book form. How does one ever expect a beginner to get to grips with it in that case!?!
Obviously Rust isn't there as it doesn't have 30 years of evolution and development like C++ does. But the rate at which it is growing and changing means it won't actually take 30 years to become the new C++. And that would be a real tragedy. What's the use of all these awesome safety features if they're in a language almost no one will be able to fully comprehend or understand?