It doesn't require regular people to be involved.

As long as the journalists, politicians, screenwriters, staffers, celebrities, and other cultural elites continue to use it to signal which issues matter, which ones don't, and how their various tribes respond, it'll continue to underpin the culture.

It already got as far as it has in the US with under 20% of the population. That's with >80% not participating. Getting that back to 90 or 95% won't matter as long as the most influential (including most influential OUTSIDE of Twitter) people stay.

The influencers are the key, and unless you are a big influencer, leaving twitter as an individual will have negligible impact. The former is big enough that the latter will stay even when all this is happening. It is indeed a medium, but it's a medium becoming more and more compromised, as we've seen over the months

So you either need influencers to shift out (which is happening, slowly. But I'm not sure if it'll be enough to "kill" Twitter) or somehow generate a new batch of influencers for a competitor. Both are hard.