I have now read two different historians recently taking different positions on niche and broad-focused histories.
In the realm of niche subjects, in Historiography (2012), Jeremy Black points out,
[Academics] have sought out hole-in-the-corner subjects that, a critic might imagine, they can invest with meaningless complexities, as defensive walls against penetration by the initiated (16).
The concept of selecting a narrow topic to act as a defense mechanism is a remarkable accusation. However, we cannot decipher the motives of historians who select such focuses. Instead, I think Black’s criticism is worth remembering, as we reflect on our own work.
On the flipside, Lukacs praises some of the niche-focused historians in The Future of History (2012),
We ought to pay more than routine respect to the genuine specialist (whether professional or amateur) because of his authentic dedication to his subject, which often amounts to more than his desire for recognition (19).
Lukacs sees a different problem, not in the narrow focus, but instead of too broad of a focus.
The broadening of historians’ perspectives so often led not to a deepening but to a shallowing of their craft. “Social” (and “gender,” “economic,” “religious,” “intellectual,” “sexual”) histories are now manifold and rampant (86).
Lukacs then goes onto to list some outrageously titled, award-winning papers. His concern is over the availability of sources and evidence to make such broad conclusions.
Between the two, it would seem that historians should select topics that are just right on the scale of niche vs. broad.