My take is a simple one: most people are interacting less on Twitter. This likely leads to people contributing less on Twitter, which leads to a downwards spiral. I see this on other social media as well.
The one exception to those interacting less are active self promoters. Self promoters, whether doing it personally or professionally, are still interacting regularly with social media such as Twitter. After all, it’s free and it’s better than doing nothing.
Overall, though, I expect there to be a decline in use of all kinds of social media, until someone can invent a social media that is more effective than what we have today. That may be a few years off.