I think it depends on how long you want the software to last for. At one end is a client wanting a quick mock up - yes use libraries. At the other end is a su

I think it depends on how long you want the software to last for. At one end is a client wanting a quick mock up - yes use libraries. At the other end is a surgically implanted heart monitor - please dont use a library that depends on an API call. Using libraries certainly gets the job done quicker (in the short term), but it adds technical debt and brittleness to any project.