Note that newer things are always downloaded less because they have been around less time (lots of people continue using old versions).

Maven stats are available to artifact deployers, but they are useless for estimating users or community size as downloads are largely from CI servers constantly downloading artifacts for testing. Download numbers are large and seesaw erratically. Unique IP counts are a little more stable but also inflated beyond relevance by CI.

I agree with your critiques, but I still don't think it negates the overall picture I see.

When I was a scientist, we were trained to look at the overall body of evidence when trying to assess a claim. Any individual study has flaws, but when we survey the literature as a whole, do we see many studies confirming a finding? Independent studies presumably don't share the same set of flaws (usually), and the more studies demonstrating something, the more likely it is to be true.

And I just haven't heard any counter-evidence. Are job postings increasing or decreasing? What's the change in MAU for Clojurians? Etc.

I looked for job/social media numbers, but it's hard to get those numbers. If you have better data, I'd love to see it.