Agreed that Great Courses has a sweet spot... they bring in great professors who are particularly engaging and good at teaching. So, much more engaging than Coursera on average but still a high level of expertise. For a tough technical subject, the lack of exercises makes GC a poor fit, but for high-quality "edutainment," I think it's a perfect balance. (I particularly liked this class on the Etruscans https://www.thegreatcourses.com/courses/the-mysterious-etrus...)
If an author/artist/celebrity you particularly love is on MasterClass, it may still be worthwhile to pay for access to their bit. But you learn much less. I took the Annie Leibovitz photography class and absolutely enjoyed it. I still think about a few things she said. But I don't think it improved my photo portraiture skills at all. If anything, it sort of demoralized me to see the incredible level of input required for portraiture at her level.
If an author/artist/celebrity you particularly love is on MasterClass, it may still be worthwhile to pay for access to their bit. But you learn much less. I took the Annie Leibovitz photography class and absolutely enjoyed it. I still think about a few things she said. But I don't think it improved my photo portraiture skills at all. If anything, it sort of demoralized me to see the incredible level of input required for portraiture at her level.