The number of domains where low-level languages are required, and that includes C, C++, Rust, and Zig, has gone down over time and continues to do so. All of these languages are rarely chosen when there are viable alternatives (and I say "rarely" taking into account total number of lines of code, not necessarily number of projects). Nevertheless, there are still some very important domains where such languages are needed, and Rust's adoption rate is low enough to suggest serious problems with it, too. When language X offers significant advantages over language Y, its adoption compared to Y is usually quite fast (which is why most languages get close to their peak adoption relatively quickly, i.e. within about a decade).
If we ignore external factors like experience and ecosystem size, Rust is a better language than C++, but not better enough to justify faster adoption, which is exactly what we're seeing. It's certainly gained some sort of foothold, but as it's already quite old, it's doubtful it will ever be as popular as C++ is now, let alone in its heydey. To get there, Rust's market share will need to grow by about a factor of 10 compared to what it is now, and while that's possible, if it does that it will have been the first language to ever do so at such an advanced age.
There's always resistance to change. It's a constant, and as our industry itself ages it gets a bit worse. If you use libc++ did you know your sort didn't have O(n log n) worst case performance until part way through the Biden administration? A suitable sorting algorithm was invented back in 1997, those big-O bounds were finally mandated for C++ in 2011, but it still took until a few years ago to actually implement it for Clang.
Except, as you say, all those factors always exist, so we can compare things against each other. No language to date has grown its market share by a factor of ten at such an advanced age [1]. Despite all the hurdles, successful languages have succeeded faster. Of course, it's possible that Rust will somehow manage to grow a lot, yet significantly slower than all other languages, but there's no reason to expect that as the likely outcome. Yes, it certainly has significant adoption, but that adoption is significantly lower than all languages that ended up where C++ is or higher.
[1]: In a competitive field, with selection pressure, the speed at which technologies spread is related to their relative advantage, and while slow growth is possible, it's rare because competitive alternatives tend to come up.
This sounds like you're just repeating the same claim again. It reminds me a little bit of https://xkcd.com/1122/
We get it, if you squint hard at the numbers you can imagine you're seeing a pattern, and if you're wrong well, just squint harder and a new pattern emerges, it's fool proof.
Observing a pattern with a causal explanation - in an environment with selective pressure things spread at a rate proportional to their relative competitive advantage (or relative "fitness") - is nothing at all like retroactively finding arbitrary and unexplained correlations. It's more along the lines of "no candidate has won the US presidential election with an approval of under 30% a month before the election". Of course, even that could still happen, but the causal relationship is clear enough so even though a candidate with 30% in the polls a month before the election could win, you'd hardly say that's the safer bet.
If we ignore external factors like experience and ecosystem size, Rust is a better language than C++, but not better enough to justify faster adoption, which is exactly what we're seeing. It's certainly gained some sort of foothold, but as it's already quite old, it's doubtful it will ever be as popular as C++ is now, let alone in its heydey. To get there, Rust's market share will need to grow by about a factor of 10 compared to what it is now, and while that's possible, if it does that it will have been the first language to ever do so at such an advanced age.