As I recall, Pluto really got into the spotlight, pre-pandemic with the course "Introduction to Computational Thinking with Julia", which as I remember went kinda viral (or maybe just in my bubble)

It was a nice course, I did the first few weeks before life got in the way. It looks like they did one more in 2020 with a focus on COVID:

https://ocw.mit.edu/courses/18-s190-introduction-to-computat...

I would love Pluto but am completely put off by the output of a command being shown above the command that creates it. Sure, maybe the whole notebook is reactive, and I shouldn't care, but I still see Pluto as producing something close to a document or web page, which I want to read from top to bottom, and can't do with Pluto. This single feature/problem has kept me away from Pluto

Pluto has been quite nice for me to use over the last few years and I even host notebooks using the SliderServer to let others run analysis and examples from the web.

These days it is so easy to just build a full fledged react website with interactive components served locally, personally I just stopped trying to build language specific UIs.