You're overstating the strength of network effects, political discussion happens everywhere.

I don’t think you understand what network effects mean. Of course discussion happens elsewhere. It is less valuable because those other networks have fewer nodes.

It isn't less valuable at the scale at which most human networks operate. People don't exclusively limit their online communications to one account on one platform, and most people aren't networking with millions of people at a time. If it were really impossible for effective political speech to exist outside of Facebook then Gab and Parler would never have been politically relevant for Trump supporters or the alt-right, when they demonstrably were.

People do limit their communications to valuable platforms. People do chose networks with significant populations. I’m not sure why you’d say otherwise but I suspect this isn’t going to be a valuable conversation so let’s end it here.