Part of what's slow is that they're type checking and compiling the code at the same time. Best practice for a project of this size would be to run type checkin

Part of what's slow is that they're type checking and compiling the code at the same time. Best practice for a project of this size would be to run type checking as a unit test and only transpile during the build. An incremental type check is also super fast, it's possible they don't have caching setup. To me this reads more like a list of issues in the deno architecture, and how they integrated TypeScript, than any issue with TypeScript itself.