Some of history’s greatest contributions have come from polymaths.
Aristotle practically invented half a dozen fields of study across philosophy. Galileo was as much a physicist as he was an engineer when he helped kick-start the scientific revolution. Da Vinci might have been even more famous as an inventor than an artist if his notebooks were ever published.
Even in the last 100 years, we have had people like John Von Neumann and Herbert Simon who have made breakthrough advances across fields as diverse as computer science, economics, and psychology.
That is, of course, not to detract from the specialists who have pushed our progress forward. In fact, until now, these specialists have far outnumbered the polymaths in both their historical ranks and their contributions.
After all, it takes a lot of time to master the depths of a specific field so that you can eventually add something that pushes it ahead. From this point of view, it makes sense that polymaths have been as scarce as they have been.