I suppose so, but very few user applications have had the same longevity. There have been numerous text editors and word processors from the same era and after it that have disappeared, yet Emacs has endured. That has to mean something.
> measuring isn't that difficult, surveys exist, and it's been ~consistently in the low single digit %.
Surveys are not a good way of measuring the health of a specific project. Not all users will respond, and the percentages are skewed by the number of participants and popularity of other options.
A better way, though still inaccurate, would be to look at the amount of activity in the project's repository, the number of contributors, and the number of packages written in Elisp over time.
Emacs' official repo doesn't keep track of such statistics, but the GitHub mirror[1] shows signs of a very healthy project. You could also check package stats[2] or the amount of Elisp projects on GH[3], and compare them to Wayback Machine snapshots from a few years ago, and notice that they keep increasing.
These are all signs that Emacs is not going anywhere. The slow but steady growth is the positive aspect I was referring to earlier. Explosive growth is not good for an OSS project.
> Yeah, that's exactly the faux elitist fantasy ...
I mean, you're entitled to your opinion, but I haven't noticed any elitism in the Emacs community. It's mostly a bunch of hackers and tinkerers who are passionate about software and improving their workflow, as you can see from this article and comments here. There's no gatekeeping since anyone is free to use Emacs how they want to use it. Help and documentation is widely available, including within Emacs itself.
So I think you have the wrong idea and an axe to grind for some reason, which I can't really help you with. Cheers!
[1]: https://github.com/emacs-mirror/emacs/pulse