Why are React component libraries so complicated compared to Svelte?

I agree most with the attribution to React being the trailblazer and Svelte/others learning from it in many ways. React paved the way for component-driven development (though to be fair you could credit Backbone Views or Angular Directives for starting the ball rolling), and that means it was always going to be the hardest to change.

Frameworks like Vue, Preact, Svelte and others benefited from React existing and causing them to ask the questions they did (how can we make this simpler? is it possible to have the feel of component-driven layouts without the VDOM?)

This comes down to React ships post compiled assets generally and Svelte libs send precompiled. This makes it much easier on library authors but also is because Svelte has built in solutions. This has tradeoffs on flexibility. Now you can be as flexible with Svelte but then you give up this simplicity.

A year and a half ago, I moved my app Nomie from React Native to Svelte (PWA) and have never looked back.

It feels like when I first started using React after living in Angular Hell for a few years - refreshing.

I recently started building an app with electron and chose svelte for front end framework. I really couldn't be happier with the choice. Svelte has been a pleasure to build with.

because its a garbage framework compared to svelte.