Except, that
1) the network effect and critical mass make it next to impossible to gain any kind of foothold: your product must be better feature-wise, and it must have the same people or interface with the old—something Facebook has no interest in (look at Ello, G+, orkut, etc). Replacing Facebook wholesale with a "better product" has huge risk;
2) when companies can take into the economy of scale, they can start making money off of aspects that are not profitable at smaller scales (think usage data, advertising analytics, etc). I could see how limiting the size, or breaking up "predatory" businesses as a potential hard-line solution;
3) the most "productive and innovative" companies are looking to either carve parts of Facebook off into new products (think how airBNB, tindr, etc, essentially came from Craigslist's boards, but now targeted) or something tangential that can leverage Facebook, the difference here being that Facebook is far more aggressive at maintaining its moat and has a more financial interest in it (they must maintain there current company size/status). It seems that even when Facebook does something poorly (events? buy-and-sell?), they can use their network effect (1) to their ultimate advantage.