Once again, people only stop using it if there is some better alternative. It's not as if people are going to stop communicating with each other.

Near a small town there was a small lake. Many people loved to swim in the lake. One year, a terrible accident resulted in harmful pollution spilling into the lake. No one swims in the lake anymore.

They haven't stopped swimming because of some better alternative. They stopped swimming because swimming conditions have changed and now it is a bad idea.

This story is directly analogous to the scenario described in the comment that started this entire sub-thread: https://news.ycombinator.com/item?id=23743161

If section 230 is repealed and social media becomes too toxic for most people to use, of course people would not stop communicating. The vast majority of human communication doesn't even occur on social media.