Except users don't switch because of network effects. None of the twitter, reddit, youtube alternatives have managed to put even a dent in them.
Time will tell how long tiktok lasts. I find as time goes on the internet is less fluid than it used to be.
Digg was a big fish in a tiny pond even as late as 2010 when it launched v4. Most people in the English-speaking world Digg targeted were some kind of online, but usage jumped as smartphones became normal. Twitter took most of that growth in use.