Drupal's front-end is screwed; where are all the Twig component libraries?

The front-end world is rapidly moving to a component-based method of building web apps. Components are reusable chunks of HTML, CSS and JS. And there are many, many pre-built libraries of components appearing: Twitter's Bootstrap and Google's Material Design to name just two.

With the new Twig Classy theme, Drupal 8 has finally solved the problems we had 7 years ago. And that's not good.

With so many easy ways for front-end developers to create robust, engaging HTML experieces, vanilla Twig and Drupal's default theme system are not good choices. They don't provide component-based solutions.

And why aren't there any pre-built Twig-based component libraries? I've googled and found nothing. This is not only a problem for Drupal developers, this is a huge problem for PHP developers.

If front-end developers dump PHP-based front-end system in favor of fully-decoupled systems, Drupal as we know it will be dead. How do we survive? And do we want to?