I pay nothing, so I’m obviously not a customer. If Cloudflare decides to stop hosting my site free of charge, I will have to find another host. In that sense I depend on them. Is that what you meant by dependant?

Not exactly.

The same is true for paying customers.

When you pay for a service, you have some leverage with them. You funded part of the service, you're a stakeholder. If they mess up, they lose your business.

When you don't pay, you have no leverage.