HTML Web Components are Just JavaScript?

Custom Elements seem designed for providing (wait for it) custom elements (markup), while framework components (old and new) put more focus on combining all the elements into reusable templates.

This distinction between “custom elements” and “reusable templates” is helpful. Many (not all) framework component authors don’t believe their consumers can be trusted with the raw materials. So they provide a templating language instead of composable pieces.

The auto-register idea towards the end of the post is compelling. If quickly defining templates with slots is what you need.