Some time ago, I would have made an argument that memes were an example of NC. But with imgflip and A.I. scraping art from publicly available sources; I'm having a difficult time considering how NC is a helpful descriptor.
An academic using a work on an educational slide for their class... an educational reason (with purpose of critique) overrides more general copyright protections; but simply for a decoration reason might now be considered a commercial use (as the class notes are part of the package of what the academic institution uses to tuition students for money).
I'd advise the artist to choose a licence system such as one of the options offered by Creative Commons or another. (Probably not MIT licence as it also allows selling of that work to 3rd parties)