The hummable thing is bullshit. Everyone said the same thing about TFA and now you’d be pressed to find a fan who denies the power of Rey’s theme, March of the Resistance, or Kylo’s theme.
That said, the quality of a score is not just the quality of its new themes. In the final film of a nine part saga, it’d be strange if what we mostly heard was new themes. It is only natural that the majority of the score is reworkings of preexisting themes from the previous episodes (if it wasn’t, people would complain). In that case, the score should be judged not just by the “hummability” of the new themes, but of the variations and implementations of old themes as well.