no web application build tools track dependencies between source files for incremental compilation

Angular builds are incremental by default.

Web development must be easy

Why should that requirement hold for web development but not for any other kind of development?

it must be possible to iterate very quickly (which requires there to not be a compilation step)

Again, Angular makes an incremental build in about a second, maybe 5 for large applications. Compare this to Java, where even simple backends require 20–30 seconds of build time.

Web application code must be simple and understandable (which requires the application to use a minimum of libraries and frameworks)

This makes no sense. Which is simpler – a function called mergeObjects from a library or a recursive function of 30–50 lines to do this without the library? Libraries’ whole purpose is making things simpler.

Web applications must be fast and not crash (which requires a compilation step […])

Ever heard of just-in-time compilation?

TypeScript, but they seem to have exhausted the supply of such individuals

TypeScript has minor-point releases about every 3–4 months. What makes you think it’s dying?

To conclude, because this post is long enough: Your comment is full of opinions, but little else.