This doesn't surprise me. As somebody who got deep into craft beer, I have always thought of Anchor Steam as being relatively mediocre. They were likely a breath of fresh air well until the 1980s, but my the early 1990s there was a burgeoning US craft brewing revival that had a solid brewery (and in most cases better than Anchor) in every US state. They also aren't the only old craft brewery in the US, generally. It'…
It's an excellent beer of its type, and IMO of any beer type. It may be subtle, but not everything has to be an big hoppy IPA, or a sweet NEIPA etc. Do you also think that Pilsner Urquell, Jever, or Budvar are mediocre?
The flavor of the beer is heavily influenced by the yeast strain and fermentation temperature, and the primary basis of what steam beer is, fundamentally, is lager that is fermented at relatively high temperature. The yeast strains that stand up these higher temperatures tend to produce lower quantities of the types of esters that produce lasting flavors in beer, and higher temperatures tend to result in a loss of important flavoring compounds which are types of volatile organic chemicals and tend to be temperature sensitive.
There's very specific, replicable, and well-understood reasons why high temperature lagers and steam beers don't taste as good as typical low temperature lagers. I do not think your representation of steam beer is accurate, and I feel I have some authority to that claim. I am a subject matter expert on beer, a certified cicerone, and an extensive home brewer.
I am not trying to diss Anchor, I'm simply stating a mere fact, which is that their beer is mediocre. Not bad, but it is certainly not a world class beer. It may have been in pre 1980s, but the current craft brewing culture has advanced far beyond most beer drinkers expectations. For the record, I am not a huge fan of IPAs, although I will drink them, and I don't think "craft beer" and "IPA" are analogous concepts. Your reply to me reveals your biases, and indicates you didn't critically engage with my prior comment.