I made my first website a few months ago (I'm an ML engineer). I tried in both Svelte and React.
I used Sonnet as a copilot the whole time and expected Svelte to be more difficult because there are orders of magnitude less training data on it.
To the contrary! The LLM tied itself in knots very quickly with React but mostly did ok with Svelte/Sveltekit. Also, the Svelte stuff it makes is usually snappier. However it does have a wider range of UI widgets it can grasp with React.
It seems that my opinion that React is horrendously and hideously overcomplicated is at least somewhat objective! Svelte has been quite pleasant.
To any devs out there that have to work with React, you have my sympathies. Compared to Svelte it's just flaming hot putrid garbage.