What's the pitch for this service? Why would I use it?
Is it businesses? Is it individuals posting for their friends?
So I made a tool to make this task a bit simpler. I used conntent to generate my weekly newsletter yesterday. You can read it here: https://stemble.substack.com/p/indian-astronauts-embark-on-a...
To answer your question, people like me are the users.
But going back to the question in your post, I suspect the reason you aren't getting paying customers is that people/companies who are reposting content across social media already have established patterns to do it and there's not a value add of switching that to your service.