Exactly. Whether or not you think that Facebook is a monopoly, none of the Democratic candidates (or at least, none of the candidates that are serious) are talk

Exactly. Whether or not you think that Facebook is a monopoly, none of the Democratic candidates (or at least, none of the candidates that are serious) are talking about making a bunch of Facebook clones. They're talking about reversing mergers that many people claim were problematic (WhatsApp and Instagram). They're talking about forcing companies to give up the benefit of 1st-party access to the platforms they maintain. That's a much more narrow, targeted change than saying, "let's just make another Facebook", which is what I see people interpreting it as.