Whitespace skipping. Svelte is a superset of HTML with meaningfull whitespaces between inline-block elements.
Typescript support. Try to write and publish any Svelte module in Typescript.
Also Svelte lacks of good tools, templates, IDE support and etc. For example: svelte-loader restarts css pipelines for ALL files in project instead of changed one. The svelte library template uses Rollup by default to bundle library in single file, all dependencies will be inlined into module and can't be deduped and shared between multiple npm modules.
Software hacker working in the industry since 2003. Currently loves: #Typescript and #Svelte. Founder of Chimera, the first makerspace in northern California.
Better implemented in React:
Also Svelte lacks of good tools, templates, IDE support and etc. For example: svelte-loader restarts css pipelines for ALL files in project instead of changed one. The svelte library template uses Rollup by default to bundle library in single file, all dependencies will be inlined into module and can't be deduped and shared between multiple npm modules.
These are "developer experience" related opinions, nothing to do with the output for the end user.
Coming to this way late, but for #3, that isn't so much of an issue anymore with pretty decent TS support (though not perfect)