I feel like the main advantage of a large standard library is already vetted reasonable default code. When using python I don't need to read through a billion blog posts and forums to find a good json library. There is a decent one already in the standard library and it basically works. If I need a better one, then I would want to go searching. I think having a sensible default out of the box helps more than it hurts. For the compile times, why would cargo make you pay for what you don't use?