An explicit goal I would personally like to see from build tools in the JS world is long term stability. I don't want my build tools to have a new major version every year. Semantic configuration improvements simply aren't worth all the churn. Adding new functionality is fine and great, but keep it backward compatible for as long as you possibly can.

This is an area where we could learn something from the Golang ecosystem. You're always going to end up with some warts in your API. Tools with warts that are consistent, documented, predictable, and long-lasting are so much easier to manage than tools that are constantly applying cosmetic revamps.