Moby Dick was a book that I was a little disappointed with. Not that it was bad, but it has been built up as the greatest English language novel of all time, and I just didn't think it quite lived up to that. Melville could have made that book half as long had he not obsessed over boring and irrelevant details regarding whale anatomy and biology. Just my opinion.
I kind of agree with you there. I think it wasn't uncommon for people who wrote about scifi and even natural subjects, to flesh out their subjects so that people who only had a small amount, if any, learning on it would be able to comprehend the story, or imagine it as if they were actually there.
He inserts a lot of philosophical wanderings. Some of that is interesting, to read how his mind works, and some of it gets tedious.
I think there could have been a bit less of both, to be honest. He did well when he was concentrating on the story, rather than the tangential content.
It is interesting to read up on him and learn that when he wrote this story, it was only popular for a short time and it wasn't until years after his death that it got the attention that makes his name recognizable today.