Stencil's is _not_ a workable platform solution. Stencil is emulating something close to slots _above_ the DOM. Stencil knows the host tree form Stencil's own component definitions, then it flattens before it gets to the DOM. This is basically just what React and every other framework does, just copying the browsers terminology. It's not compatible with anything but Stencil.

In the real DOM you need to know which element from project _from_. The <slot> itself is only half the connection. In a light-DOM only document full of <slot>s you won't know which elements to project where.

> The problem with the browsers API is a lack of an understanding on how to design good ergonomic APIs for the end user.

This could be slightly true, but the statement also misunderstands the role and priorities of standards. When adding new capabilities to first priority is to make something possible at all, and coherent with the rest of the platform. Making a sugary high-level API is often left to libraries at first, and is exactly what libraries like Lit are.