Kid_A - the answer to the question “did a #1 record ever mean anything?” is:
well, sometimes.
Sometimes you know right then - like when a whole new genre (new to the pop charts anyway) hits number 1, like metal (Quiet Riot - crap, but showed where tastes were going at the time), new country (ditto) or rap/hip hop.
Or when an artist just dominates - like when the Beatles had all top 5 singles positions in '64 or the BeeGees (including 1 song they wrote but didn’t record themselves, IIRC) in, when, '75?
Or in hindsight, when certain artists got enough money from a hit record to do fund their explorations into other areas.
For the most part, Barnum was right (paraphrased) - “no one ever lost money underestimating the taste and intelligence of the American people”