>Creating complex type definitions for more generic components is hard and require knowledge about internals.

This is what turned me off of Svelte initially. Usually when I make websites I start by defining some primitive components like <Button> or <TextInput>. I could not figure out how to type my <Button> component so that it takes every single attr and event that a regular <button> takes plus some extra attrs that I want to define (theme, size, etc.) This is trivial in React so I was surprised that it didn't really seem possible in Svelte.