In business, cross-fertilisation is the source of all kinds of innovations: fibres inspired by spider webs have become a source of bulletproof fabric; practically every mobile phone also seems to be a computer, a camera and a GPS tracker. To come up with such ideas, you need to know things outside your field.
Over-specialisation, eventually retreats into defending what one has learnt rather than making new connections
But polymathics would not just be another name for innovation. It would, I believe, help build better judgment in all areas.
So I like to say, we need to build our reputations, and display our ‘expertise’ AND be able to keep learning and follow a wide range of interests.