jQuery plugins depended on jQuery, and when jQuery went out of favor, they ended up in the junkyard.

There is all sorts of componentry built exclusively on React, limiting it to React-based sites. As React goes out of favor, they will end up in the junkyard. (Same with any framework-specific extension.)

But with Web Components... it seems like the story will end differently. If they are built without dependencies, they might just live as long as the web does.