The number of such domains has gone down over time, and will probably continue to do so.
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.
So e.g. the silver bullet characteristics reported by Google among others in "More fast and fix things" ?
https://security.googleblog.com/2025/11/rust-in-android-move...
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.
[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.
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.
Notice that your pattern offers zero examples and yet has multiple entirely arbitrary requirements, much like one of those "No President has been re-elected with double digit unemployment" predictions. Why double digits? It is arbitrary, and likewise for your "about a decade" prediction, your explanation doesn't somehow justify ten years rather than five or twenty.
Why mistakenly? I think you're confusing the possibility of breaking a causal trend with the likelihood of doing that. Something is predictive even if it doesn't have a 100% success rate. It just needs to have a higher chance than other predictions. I'm not claiming Rust has a zero chance of achieving C++'s (diminished) popularity, just that it has a less than 50% chance. Not that it can't happen, just that it's not looking like the best bet given available information.
> Notice that your pattern offers zero examples
The "pattern" includes all examples. Name one programming language in the history of software that's grown its market share by a factor of ten after the age of 10-13. Rust is now older than Java was when JDK 6 came out and almost the same age Python was when Python 3 came out (and Python is the most notable example of a late bloomer that we have). Its design began when Java was younger than Rust is now. Look at how Fortran, C, C++, and Go were doing at that age. What you need to explain isn't why it's possible for Rust to achieve the same popularity as C++, but why it is more likely than not that its trend will be different from that of any other programming language in history.
> Why double digits? It is arbitrary, and likewise for your "about a decade" prediction
The precise number is arbitrary, but the rule is that the rate of adoption of any technology (or anything in a field with selective pressure) spreads at a rate proportional to its competitive advantage. You can ignore the numbers altogether, but the general rule about the rate of adoption of a technology or any ability that offers a competitive advantage in a competitive environment remains. The rate of Rust's adoption is lower than that of Fortran, Cobol, C, C++, VB, Java, Python, Ruby, C#, PHP, and Go and is more-or-less similar to that of Ada. You don't need numbers, just comparisons. Are the causal theory and historical precedent 100% accurate for any future technology? Probably not, as we're talking statistics, but at this point, it is the bet that this is the most likely outcome that a particular technology would buck the trend that needs justification.
I certainly accept that the possibility of Rust achieving the same popularity that C++ has today exists, but I'm looking for the justification that that is the most likely outcome. Yes, some places are adopting Rust, but the number of those saying nah (among C++ shops) is higher than that of all programming languages that have ever become very popular. The point isn't that bucking a trend with a causal explanation is impossible. Of course it's possible. The question is whether it is more or less likely than not breaking the causal trend.
Lets take your Fortran "example". What market share did Fortran have, according to you, in say 1959? How did you measure this? How about in 1965? Clearly you're confident, unlike Fortran's programmers, users and standards committee, that it was all over by 1966. Which is weird (after all that's when Fortran 66 comes into the picture), but I guess once I see how you calculate these outputs it'll make sense right?
Only because they've achieved that 10% in their first decade or so, but what I said is the case for all languages, big and small alike (and Rust doesn't have this problem because it needs a 10x boost to approach C++'s current market share, which is already well below its peak). But the precise numbers don't matter. You can use 5x and it would still be true for most languages. The point is that languages - indeed, all technologies, especially in a competitive market - reach or approach their peak market share relatively quickly.
You make it sound like a novel or strange theory, but it's rather obvious when you look at the history. And the reason is that if a technology offers a big competitive advantage, it's adopted relatively quickly as people don't want to fall behind the competition. And while a small competitive advantage could hypothetically translate to steady, slow growth, what happens is that over that time, new alternatives show up and the language loses the novelty advantage without ever having gained a big-player advantage.
That's why, as much as I like, say, Clojure (and I like it a lot), I don't expect to see much future growth.
> Clearly you're confident, unlike Fortran's programmers
Yes, because I have the benefit of hindsight. Also, note that I'm not saying anything about decline (which happens both quickly and slowly), only that technologies in a competitive market reach or approach their peak share quickly. Fortran clearly became the dominant language for its domain in under a decade.
But anyway, if you think that steady slow growth is a likelier or more common scenario than fast growth - fine. I just think that thesis is very hard to support.
This predicts nothing in particular, for any outcome we can squint at this and say it was fulfilled, so in this sense it's actually worse than the XKCD cartoon.
It's not that it's a novel or strange theory, it's just wrong.
> if a technology offers a big competitive advantage, it's adopted relatively quickly as people don't want to fall behind the competition
Yeah, no. See, humans have a strong preference for the status quo so it isn't enough that some technology "offers a big competitive advantage", they'd usually just rather not actually. Lots of decision makers read Google's "Move Fast and Fix Things" and went "Yeah, that's not applicable to us [for whatever reason]" and moved on. It doesn't matter whether they were right to decide it wasn't applicable, it only matters whether their competitors reach a different conclusion and execute effectively.
Okay. Can you provide an example of a language that steadily and gradually grew in popularity over a long time (well over a decade) and that this slow growth was the lion share of its market size growth? You say "it's just wrong" but I think it applies to 100% of cases, and if you want to be specific when it comes to numbers, then even languages whose market share has grown by a factor of 5 after age 10 is a small minority, and even a factor of 2 is a minority.
> Yeah, no. See, humans have a strong preference for the status quo so it isn't enough that some technology "offers a big competitive advantage", they'd usually just rather not actually.
Except, again, all languages, successful and unsuccessful alike, have approached their peak market share in their first decade or so. You can quibble over what I mean by "approach" but remember that Rust, at age 10+, needs to grow its market share by a factor of 10 to even match C++'s already-diminished market share today.