The more exceptional the talent, the longer it takes for the world to discover and understand it.
Literal
Extraordinary talent [subject-が] excellent [the more-ば] [the more-いるほど], public people [subject-が] that [object-を] discover and understand [purpose-のに] long time [subject-が] takes.
~ば~ほど means 'the more X, the more Y' — one of the most expressive comparative constructions in Japanese. 非凡の才 ('extraordinary talent') is a formal, literary phrase. The sentence reads like an aphorism about genius and public recognition.