My personal understanding (as a web developer) had always been, someone who is "good enough" is someone who can build a system from the ground up, with the capability to handle requests at high capacity and manage performance. BUT, this would just be an advanced CRUD app and I fail to see how that would reach a salary of $500,000 a year.
It looks like ShellyPalmer has a special focus on machine learning and data science. Perhaps their requirements are beyond what I am even aware of.