I haven’t read the book which is the subject of this interesting Atlantic article, but would like to offer some thoughts.
First, even post-Prohibition, American beers must have had plenty of taste. Look at A.L. Nugey’s table of beers circa-1936 I posted a few days ago. Those beers were hopped at .5 lb to upwards of 1 lb per (American) barrel, which is much, much more than the modern norm – I’m speaking here of the typical mass market beer, not the craft segment. It’s rather more than English bitters were achieving in the period leading up to the craft beer onset in the U.K.
Even though most of those beers used some rice and corn adjunct (or sugars), they had to be far more impactful on the palate than the typical modern light beer or standard macro offering. This is due both to the much larger hop content than today but also the probable average lower percentage of adjunct used as compared with modern mass market beers.
Sam Adams Boston Lager uses about 1 lb hops per U.S. barrel and is based on an 1800’s recipe of the founder’s ancestor: would anyone claim it is bland? Would anyone claim Pilsner Urquell, the “first” blonde lager and 4.4% abv as it was in the 1800’s, is bland? The American Budweiser in the 1800’s surely tasted much closer to both these beers than it now does… I don’t see that German immigration or lingering Volstead attitudes had much to do with the decline of beer flavour. The lowest alcohol level permitted in some states after 1933, 3.2 alcohol by weight, is about 4% by volume, fairly respectable. Foster’s lager, a large-selling brand in English pubs, is currently 4% abv. And many states post-Volstead had higher limits on beer abv or no limits.
I believe the blandification of North American beer started mainly in the post-war era and gathered pace from the 1950’s in particular. This was for a variety of reasons: cost-savings under more sophisticated business strategies (use less or less costly materials = make more money), expanding the beer market to include more women and young people, and foremost, industry consolidation. Also, the U.S. and Canada had a corn crop, thus corn (or rice) became acceptable to use as an adjunct to barley, for which too there were technical brewing reasons at the outset, e.g., they promoted clarity.