Edit: To clarify, Clojure is mostly a dead language that didn't have any innovations by itself, but it did influenced many programmers(the creator is good at marketing). It helped push forward the FP mindset into the users of other mainstream languages(js, python, java).
This suggests we clarify what is meant for a language to be "mostly dead". If we consider size compared to total market or trajectory we may ultimately conclude that a project for example Clojure is "mostly dead" compared to JavaScript or java.
However this isn't ultimately the most useful metric. Would you for example select a restaurant based on the reviews and the cuisine or to total annual revenue of its parent company. If your metric suggests you forego surf and turf at a local diner in order to eat a Whopper you may be asking the wrong questions.
For your consideration here is a better one. A language is alive when its ecosystem is likely to receive enough interest and talent to continue to develop enough to allow its users to continue to accomplish useful goals. Being embedded in 2 of the top platforms and being able to reuse those libraries is a factor. Relying on these host platforms means that it can remain alive indefinitely while being useful to only thousands instead of millions as long as it drives enough interest to pay the salaries of the dozens who develop the core and the hundreds that write useful tools.
It has less market share than perl or delphi (make your own judgement). It was really hyped(rightfully so, a practical lisp for production use? fun! sign me in) then declined fast.
Like most(ly dead) languages, it still has its followers, in the case of clojure, mostly a cultish group (my impression from r/clojure and other forums).
Can you explain and support the idea that the number users using the language productively declined? The state of Clojure survey seems to have held steady at 2500 from 2015 to 2020 with 60% saying they used it for work in 2015 vs 69% saying they used it for work in 2020.
Going back to 2010 we see less than 500 respondents and only 27% using it for work. A charitable assumption is that it grew substantially between 2010 and 2015 and held steady between 2015 and 2020.
Edit: To clarify, Clojure is mostly a dead language that didn't have any innovations by itself, but it did influenced many programmers(the creator is good at marketing). It helped push forward the FP mindset into the users of other mainstream languages(js, python, java).