The most crucial thing that Make lacks is multiple outputs and precise control over execution. When you're debugging/developing a large and expensive workflow, you absolutely must have the ability to say things like: - run only this step, I'm debugging it - I've changed implementation of this step, re-build it and everything that depends on it - build everything except this branch, it's expensive and I don't need to rebuild it that often (example: model training)

Other examples of intractable problems in Make would be timestamped dependency resolution between local and HDFS files. If Make can't look at HDFS, it can't say if the step needs to be built or not. I don't think you can fix it with external commands.

But generally, search for intractable problems is a futile one. Remember, everything you can code in Java, you can code in a Turing machine. :)