True, I did not enumerate them. Adds another step to development and generally adds complexity would be other perceived downsides.

I'll note that most of the upsides are also subjective.

Deno/bun support TS natively, and Node is also adding support.

https://github.com/nodejs/node/pull/53725

> adds another step to development

I never understood this. It takes maybe 10 minutes to set up TypeScript in a project if you’ve done it before.

Compared to all the other times involved (time to learn typescript, time saved debugging and writing tests for type errors) the setup time is a total non-issue.