Li Jin recently published 16 Key Metrics for the Passion Economy, in which she outlined the various measures of success of startups in the space.
The first group focuses on the primary success metrics of the creators themselves - how well they are moving through the funnel. These include per creator metrics (% free supporters to becoming paid), to aggregrate views of their ecosystem (% creators have reached a certain threshold).
Each creator is a business, so they have to look at the growth of their business (typically through engagement metrics) and the revenue that audience is driving. There are also a number of interesting metrics to measure organic growth and network effects.
Now that every creator is being given the tools that many startups didn’t even have a decade ago, we can probably expect an massive increase in demand for skills that help software-powered businesses grow.