Obviously it says nothing about the number. If we look at the number of downloads of the current version, it's ~40000. Now many systems may download it multiple times. So the number is not an indicator for a large user community.
> Wonder why you didn't mention anything about Clojurists Together, doesn't fit your narrative? https://www.clojuriststogether.org/members/
It 'fits my narrative' well. Just count the number of the members.
Don't get me wrong, that's all fine and useful in a small community, but to claim a handful of companies and a few hundred people is an indicator of a mainstream popularity is just massive overselling and looks 'silly' (to quote you again, sorry).
Mainstream: large relative and absolute numbers of users.
For example the Porsche Taycan (-> Microsoft) is not a mainstream car, even though Bill Gates has one and Porsche is an incredible profitable company. https://www.economist.com/business/2019/09/12/porsche-is-sma...
It obviously does because people are using these libraries in their projects. As I noted, it's an indirect measure, but it still gives an idea of the usage. And Open Collective was just announced last month, so not sure what point you were trying to make there. Wonder why you didn't mention anything about Clojurists Together, doesn't fit your narrative? https://www.clojuriststogether.org/members/