This kind of misses the point. Facebook designed its product, services, and its entire business model around the need for serving you ads. The idea of a Facebook "without ads" almost seems like a contradiction in terms, because if the need to serve you ads wasn't baked right into the service's design it would never look or work the way it does.

I may be willing to pay some nominal amount of money for a service that fulfills Facebook's ostensible mission of "connecting people" (however vague that is). This would probably have wound up looking a lot more like Facebook's original iteration, which was functionally just a personal homepage and message board.

A service that made it free to view, like, and share content but charged a fee on the order of a postage stamp to post stuff (up to a certain amount of stuff) would probably have much less reach, but a way way waaaay higher signal to noice ratio. I'd happily pay $0.45 cents to send a party invitation or share a photo album to a service like that assuming we don't have some race-to-the-bottom situation where nobody will pay.