I'm just grateful it's a duopoly and not a monopoly. Can you imagine how much worse the situation would be if one company soft-owned the entire space the way Facebook does with social media?
I'm not sure how facebook is a monopoly on really any level (see tiktok, twitter, youtube, snapchat, etc etc). Visa Mastercard duopoly also has 10x the barriers of entry that social media has.
My reasoning was that, across all Facebook-owned properties, they have ~7 billion MAU. All their top competitors combined are roughly half that. [1]
This is all illustrative, of course. My salient point is that monopolies are only really held in check by the law. In this case, at least there's a significant competitor.