They would likely employ advertising, just as YouTube does. Are you saying it's not profitable to run a video hosting service?
YouTube is evidence of that already.
A more straightforward way to accomplish this in areas where content size is large/expensive is to disallow coupling client creation with data hosting, and data vendors would license access to their data to client creators.
Bundling becomes anti-competitive at a certain network size, because there becomes no meaningful way to create a competitor network. The essence of what makes capitalism effective is competition driving costs lower, and in many areas in tech we have very little competition due to large network effects.
Keep in mind Capitalism != Free Market. A fully free market is a form of Capitalism that has no laws, and no impediment to monopoly formation. Competitive Capitalism with minimal laws to encourage competitive where large network effects or monopolies form is far more societally beneficial in the long run.
Decoupling client/data has already been done many times in the past in analogous situations, e.g. when movie producers were not allowed to own the theaters where the movies were played, giving a much more equal footing to smaller content producers.