The difference being that C++ developers have around 6 years time to get acquainted with each version.
The 3 years for each ISO revision, plus around three until the standard is actually usable in a portable way.
My old dusty non-maintained MFC applications still compile on latest Visual Studio.
* The new lifetime model (non-lexical lifetimes)
* Async fn
* Procedural macros
* ? operator
* Import name resolution changes
* impl Trait
* C-style unions
Here's the list of features added in C++17 and C++20:
* constexpr if
* Modules
* Structured binding
* Type deduction helpers
* Coroutines
* <=> operator
* Concepts
* Expanded the set of expressions and statements that qualify as constexpr to the point that it's a very different feature from what it was in C++11.
In the same amount of time, C++ has added roughly the same number of features, but I would qualitatively say that C++'s feature additions are more impactful than Rust's feature additions, especially in terms of making newer code unrecognizable to programmers used only to the old version.
That's what I meant by pace versus cadence--overall, C++ has changed more, but it tends to change in triennial bursts instead of every six weeks.