alt Hacker NewsA Jack of all trades is a master of none, but better than a master of one because he has broad, intersectional knowledge. Academia is designed for specialization and the more you specialize in something the more you lose the forest for the trees.
Everything looks like a nail if you are a hammer and all that.
While the extreme "master of one" exists, most academics I know have cross-cutting interests.
We also shouldn't forget that the vast majority of politicians today are lawyers by education. To whatever degree your assumption holds, it is true of the status quo today as well. Even in that case, having a more diverse set of "masters of one" would be an improvement.