The biggest pressure against polymaths is the structure of the modern university. From department organization, mentoring, battles for funding, it is very difficult to find an encouraging environment if you don't stay within a narrow niche.
As an aside, I feel like most interesting innovation in academic computer science happened before the field was full of computer scientists. In the early days, the field was a meeting point of trained mathematicians, physicists, economists, engineers, and linguists, and innovation flourished. To some extent, I credit people exploring and communicating about similar concepts from multiple perspectives. Now, everybody in academic CS has taken the same path in life, and it makes things quite boring.
As an aside, I feel like most interesting innovation in academic computer science happened before the field was full of computer scientists. In the early days, the field was a meeting point of trained mathematicians, physicists, economists, engineers, and linguists, and innovation flourished. To some extent, I credit people exploring and communicating about similar concepts from multiple perspectives. Now, everybody in academic CS has taken the same path in life, and it makes things quite boring.