The person you’re replying to was just being sarcastic. Which is why they mentioned James Joyce not having “worldbuilding” (worldbuilding being a commonly lauded trait by people who have never read anything other than high fantasy novels).

Moby Dick simply just is great literature. It’s so resolutely great literature that it’s one of those rare works where it simply doesn’t matter if anyone claims otherwise, because the scale of consensus on the matter is simply overwhelmingly tipped towards it being great. Someone arguing that it isn’t great would just come across as white noise. There’s not a meaningful criticism to make outside of some dull “badlit” denigration of the departures it makes from moving the plot forward. It’s often considered to be “the” American novel, if you’re someone who thinks vague titles like that carry any weight. If nothing else, it’s one of the few American novels of that period which held its own against the great Russian literature (Dostoevsky, Chekhov, etc.) of the 19th century.