If that’s what this video is about then it’s a lie (I’m not going to watch that bait). Svelte did not move away from Typescript. Svelte just moved from TSs custom syntax to TS-in-JSDoc. They are still using the same types and TS compiler to fully enforce type checking their code.

Their reason isn’t that TS is bad, just that the IDE experience is bad redirecting you to .d.ts instead of source files for libraries.