Idleness refers to the state of being idle, inactive etc when it comes to economic prosperity and growth idleness is one thing that fights against it from the times of old till now any individual or even country that has had economic power is one that was not idle but always active engaging in one activity or the other that will be helpful to the economic growth of that person or country
As an individual, you can be active, not idle, but engaged in the wrong activities that, even with all your engagement, will not lead to any sort of economic progress.
This is why you must be selectively involved and pick the activities that you choose to give your time to because some activities may seem productive, but in the actual sense they are not productive, just a waste of time.