Blank (i): A. disparagement
The sentence establishes a parallel with "Acclaim and (i) ______ flow readily," where "acclaim" corresponds to the response to masterful buildings. The blank must name the response to flawed buildings - something that flows readily and is the opposite of acclaim. "Disparagement" (criticism, belittlement) fits perfectly. "Approbation" (praise) is a synonym for acclaim, not its opposite. "Veneration" (deep respect) is even stronger praise, the wrong direction entirely.

Blank (ii): D. exacting
The sentence pivots with "But what of structures that amalgamate...?" signaling a contrast. Unlike straightforward cases where judgment flows readily, mixed structures make the critic's task more difficult. "Exacting" (demanding, requiring great care and precision) captures this. "Perfunctory" (done without care, superficial) is the opposite - a mixed building would not permit a perfunctory review. "Congenial" (pleasant, agreeable) misses the sense of difficulty entirely.

Blank (iii): H. winnowed from
The critic must separate good elements from bad ones. "Winnowed from" means to separate and remove the worthless parts from the valuable - exactly the action of distinguishing ingenious gestures from derivative ones. "Commingled with" means mixed together, the opposite of what the critic must do. "Subordinated to" means made less important than, which doesn't capture the act of separation and sorting that the context demands.