This is, in a way, an answer to The Dunciad.
In a way, Pope's judgement in that last volley in the Querelle des Anciens et Modernes is inerrant: he's correct in seeing the new world of Theobald and Bentley as a rejection of what had been, until that point, the agreed-on values of culture and civilization. In place of a reading of Attic and Augustan texts as a guide to a baseline for culture, we have instead
To sound or sink in cano, O or A,
Or give up Cicero to C or K.
Let Freind affect to speak as Terence spoke,
And Alsop never but like Horace joke:
For me, what Virgil, Pliny may deny,
Manilius or Solinus shall supply:
For Attic Phrase in Plato let them seek,
I poach in Suidas for unlicens'd Greek.
In ancient sense if any needs will deal,
Be sure I give them fragments, not a meal...
For Pope, Theobald represents the same model as applied to modern culture; a reduction to meaningless details.
Yet in a very real way Pope takes a stand on a hill with a weak foundation. He takes it for granted that the key to effective reading is the application of innate good taste. As a corollary, he rejects the need for expertise to determine issues which are no longer (or perhaps never were) obvious.
Theobald introduces to the study of Shakespeare an attention to details of the past which has started to be applied to classical authors. In doing so he not only is part of an ongoing assimilation of Shakespeare to the status of a classical author, but a key player in a transition where scholarship tries to work with the works of the past on their own terms. In the future to which Theobald points are the editions of (for example) Malone. (It really does matter how we pronounce the poetry we read if we want to understand how the author meant his effects. Recovering the digamma does affect our understanding of Homeric scansion. And understanding Shakespeare in terms of his own time shifts him from a "natural" poet whose roughnesses are imperfections to be elided away by emendation to an accomplished writer on his own terms whose linguistic frame was different from that of the 18th Century.)
The argument of the book, well supported, is that Theobald was not a dunce, and deserves a refurbishment of his reputation.