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The difference is that in this case Facebook controls the complete platform including access to the customers that your startup requires to survive and prosper.

Paypal had independent access to markets. It just grew fastest via eBay because it solved a problem that eBay initially could not.

Clone PC makers had independent BIOS and MS-DOS so IBM could not snuff them. It finally lost when it tried to move PC users to the PS/2 platform and customers would not follow.

Microsoft negotiated and blocked exclusive licensing and control by IBM of MS-DOS before the first IBM PC shipped.

So yes, you can succeed if you have a way out of the inherent trap of being just another sharecropper. And to do that you better have negotiated a much better deal where you have options that cannot be easily blocked that are not being offered to everyone else. But you cannot expect to win much if you accept the publicly offered terms.

Facebook's terms of use for their platform allow them to cut you off from "your passionate users" at Facebook's whim.