"As of 15 February, 2023, community statistics on the language's official website show more than 123 million projects shared by over 103 million users, over 804 million total projects"[1]
Compare to GitHub:
"As of January 2023, GitHub reported having over 100 million developers and more than 372 million repositories"[2]
Of course, the average Scratch user is very different from the average GitHub user, and the average Scratch project is very different from the average GitHub repo - but the numbers don't lie (probably).
[1] https://scratch.mit.edu/statistics/
[2] https://github.blog/2023-01-25-100-million-developers-and-co...
Edit: Somewhat tangentially, bear in mind that Scratch publicly launched in 2007. The first generation of Scratch learners are now adults with jobs in-industry, who appear from time to time on the front page of HN ;)