I wonder if the advent of electrical refrigeration made possible not only the wider distribution of national beer brands but also the gradual lowering of quality of those national brands. Over the course of a relatively few decades, the populace grew accustomed to drinking beer cold -- which meant that the populace grew used to tasting fewer of the beer's flavors, because of that coldness. Once the popular palate's expectations were lowered, beer quality could be altered in ways that "had no effect" on flavor.
Some beer recipes presumably remained the same, from the later 1800s, when several famous brands reached for and achieved national prominence, through to the later 1900s: yet even if the recipes were "the same" on paper, the brewing industry's practices and procedures and additives changed, so that the results changed.
What was it like to drink, for instance, a Pabst or a Budweiser in the 1890s? Production had increased to an unprecedented degree -- yet the grains were being grown without intensive use of industry-produced chemicals, on soils that were relatively unstressed. The flavor must have been marvelous -- or it would have been, could our contemporary taste buds be transported back for a sip of that bygone beverage.
To the then-contemporary taste buds, though, it was simply good beer.