I'm torn between it probably being a good thing to have some more competition if Facebook's market dominance were lessened, but also wondering how it can be rep

I'm torn between it probably being a good thing to have some more competition if Facebook's market dominance were lessened, but also wondering how it can be replaced. If they were to pull out of Europe (which I can't see happening), then who would replace them - you would have to either be a Euro-only social network or just a more privacy focussed global social network, both of which have questionable profitability I imagine.