It's the price you pay for having a declarative language that lets the language implementation pick from a large universe of equivalent ways to actually compile

It's the price you pay for having a declarative language that lets the language implementation pick from a large universe of equivalent ways to actually compile and run the code. You now have to know how to tune the thing, and that requires having either specialist knowledge of the implementation in question, or the skills to find and apply that knowledge quickly. The value this provides is making development very agile (in the dictionary sense of the word).