Clojure never had much usage on real world projects. It cannot be extinguishes as it never took of.
I'm not sure what you mean by "never took off" but thousands of developers around the world, myself included, have made their living just writing Clojure code for many years. So, it has certainly taken off for them. And there are many, many companies using it all over the world. I live in a town of about half a million people, so not super big, and there are about 12 companies primarily operating on a Clojure codebase.
Amazon also uses Fortran, Assembly, Awk, Mosel, VBA, K, and Bash, but nobody is going around claiming they have much usage on real world projects.
Walmart is using Clojure for their checkouts as well https://www.youtube.com/watch?v=av9Xi6CNqq4
Boeing is using it in the onboard control systems for the 737 Max https://www.youtube.com/watch?v=iUC7noGU1mQ
It's not some obscure microservice that some intern wrote over the weekend, these companies are using the language for critical applications, and the feedback from these companies is positive.
If anybody led you to believe that their team did “online checkout”, but didn’t care to explain how small of a cog they were in an extremely complex system composed of hundreds of services, then you were grossly misled.
If someone doesn't want to use it for this reason or that, it's their loss not ours. Those who need to find Clojure eventually will, because there is nothing else like it.
You wouldn't want Clojure, Java or any languauge with GC running in a pacemaker either. Those are all also very important distinctions.
C++ actually proved difficult to adopt over C. The language is too difficult and the tooling is too poor. It's too hard to run a static analysis or prove 100% code coverage.
With regards to tooling, the windows visual studio experience for C++ is widely counted as one of the best development setups in the industry for any language. I know lots of people working in other languages that envy what C++ developers get.
> Edit2: it's not me who needs to prove lisp is useful. At least, be honest with yourselves.
This is one of the great fallacies among the naive in their logic.
For example: I know for a fact that you never wear underwear. I don't have to prove this, because it is a fact. If you don't agree, then it is up to you to prove otherwise.
See how that reasoning works?
Thank goodness the criminal justice system in most Western nations doesn't rely on that logic.
Make wild claims, then expect others to do the hard work.
For decades, there have been rumors about the death of dynamic languages in general. And yet the decades pass and not only do those languages continue to flourish, but others come along and get popular too.
Clojure just turned 10 years old and I see no signs of it slowing down. They did consolidate their 2 major conferences in the States into just one annual conference, so there's that (which may not mean anything). But I am in a large city and companies keep appearing and starting up with Clojure as their key language.
With Clojure, it's an oddball because it is very simple and very powerful. Oftentimes, simple languages are not so powerful, and powerful languages are not so simple. But with Clojure, you can very easily get yourself into the situation of having extremely dense logic in just a few lines, where another language might easily take 10x (or more) lines to accomplish the same. This leads to code that can indeed be difficult to read later, especially if you are on a team and others must help maintain it. The Clojure community has come up with some excellent solutions to this problem, most recently the Clojure.spec library which is gaining wide adoption, which not only makes such "cleverness" easier to understand when reading it, but also makes a codebase automatically testable with property generators, which is a major feature. But your point about readability is always going to exist with a language like Clojure if it isn't written with a team in mind. That doesn't take away from its power though, in my opinion.
However, there is one particularly indispensable tool that Clojure offers that I have not seen anything to meaningfully compete with for productivity, and that's ClojureScript. Writing a front end with Reagent or even the alternative libraries is such a major win over everything else I've tried. I've worked a bit with Elm, Typescript, Reason, Bucklescript -- I am so spoiled by the extremely fast turnaround and easy interaction with very powerful features like React in Clojurescript that I don't see anything on the horizon that will come close to replacing that workflow for now. Perhaps some day something will come along to shine an even brighter light on how front ends can be developed, but for now, ClojureScript remains one of the most significant contributions to the software industry in many, many years.