If you take to time to set up incremental compilation, it's really quite fast. For reference, updates to the vscode repo (~5k files) take generally <300ms to recompile, and even incrementally updating after pulling in a batch of hundreds of commits takes only ~10 seconds.

It's concerning to me that the deno folks chose giving up on type safety over figuring out how to set up their development environment to better meet their needs.

True, with the Angular CLI I believe this has even the default for a while locally but I have yet to encounter incremental compilation during CI e.g.

Also running tests is quite time consuming of you do not run them in parallel.

I guess bazel would be a good fit with Typescript.

As for deno, I did not follow the topic but I hope they at least annotated with JSDoc so developers can get some linting.

in a big application you can throw scala and others into the mix and typescript would still be way slower.