I don't get y ppl applaud Dickens Joyce Proust but frown on long sentences?

The king of long sentences in my book (no pun intended) is Charles Dickens. not only Dickens, but Marcel Proust, James Joyce, William Faulkner. They wrote sentences that sometimes went on for pages at a time. What i don't get is that I'm writing a novel and the first chapter has been edited and one of the things my editor and teachers have told me is that the sentences are too long. NOT that they don't make sense, or that they are grammatically incorrect, but just that they are too long and there are too many of them. Now WHY can u pleaze tell me do we celebrate, LOVE writers like Joyce Dickens Proust Faulkner and yet discourage, and i would even say hate ppl like me who ENJOY using long sentences???