I think Svelte/sveltekit (especially) has really pushed a lot of the ecosystem forward and I love the effort made to exposing platform primatives more explicitly while attempting to make the framework disappear. I think the store mechanism is really great but I have noticed a few usability complaints coming from react land.

The main one for me is typing props for a component feels extremely wack. In react I have a function, that function takes a type, I export that type and can import that type. In svelte I'm exporting the props individually? It's annoying to get the type declarations in one spot and make that easy to import for other components to use as intermediate typing. This is one of those things that I didn't even think twice about until my project reached a medium size and had multiple developers building out different portions -- it's inconvenient to scale and none of the workarounds feel good.