SCRAPE THE SERVER LOGS, THEY CAN'T TELL AND YOUR USERS WILL THANK YOU.
Furthermore, if you look at the LibreJS project page [3] and then click on the link of the Firefox extension [4], the user count will explain that the vast majority of people on the web won't have it installed and perhaps won't even have heard of it.
If anything, extensions like uBlock Origin [5] would be of more concern in regards to the client side analytics, since they usually have more downloads.
In summary: unless you're running a site that's tailored particularly for free software enthusiasts or the crowd that are overwhelmingly likely to disable JS, then no, it won't matter.
Sources:
[1] https://stackoverflow.com/questions/9478737/browser-statistics-on-javascript-disabled
[2] https://deliberatedigital.com/blockmetry/javascript-disabled
[3] https://www.gnu.org/software/librejs/
[4] https://addons.mozilla.org/en-US/firefox/addon/librejs/
[5] https://addons.mozilla.org/en-US/firefox/addon/ublock-originEither way you're going to have to do some work with the data (and probably include statistics from the server side anyway.)
Server side logs could be useful for detecting abnormalities indeed, but for getting overall usage statistics, i doubt the occasional bot or user with disabled/blocked JS execution is at all relevant.
Essentially, if 1-5% (example number, the actual one probably differs) of the general population have ad blockers, or will not execute the JS that you want them to, then it stands to reason that the demographics of your site would also be representative of the overall picture.* As for how those numbers would be figured out in the first place - i'm sure that plenty of larger sites and parties with more resources have figured out ways to aggregate this information and have published it (like the statistics in the posts above). So essentially you don't have to look, because others already have.
*unless the audience of your site is really niche and therefore differ in this regard from the average. For example, Facebook would be a decent representation, whereas Hacker News would not.
Wikipedia or other sources might tell you that "approximately X% of the devices that use e-commerce sites are mobile phones" which would be useful in figuring out that you should have a responsive site, but analytics could tell you "this one element doesn't display properly on mobile devices and therefore 95% of the users on mobile devices don't use this particular functionality".
But I get a LOT of dumb bogus bot traffic. On some pages it would dwarf real traffic. I don’t even bother to log the requests that hit the cache.