My answer would be the ecosystem, let's say you've to implement a note editor, a calendar and a dnd module and what not. You move fast because it has already be

My answer would be the ecosystem, let's say you've to implement a note editor, a calendar and a dnd module and what not. You move fast because it has already been solved. And you don't reinvent the wheel. Also have a look at the frontend iceberg there's a lot more to frontend systems.