I think this is the primary reason #Tumblr has not implemented #ActivityPub on their site.
They are making silly business decisions (charging money to add a custom domain), which screams of desperation.
Reading this makes think Tumblr will probably not join the #Fediverse this year.
👉🏾 Tumblr is losing $30M each year, CEO says https://techcrunch.com/2023/07/12/tumblr-is-losing-30m-each-year-ceo-says/
The big issue I'd see is that the skillset needed to operate a site like Tumblr might not be very front and center in that group of superusers.
From technical through organizational skill, it sounds like a job one can't really do as a side project, and I'd worry that users wold focus on their personal goals for the site without having the abilities to actually implement those goals.