There is a “clean” version of HF for those that find it offensive in a modern context, but Twain deliberately used that word to help drive the point of the novel. That some people today condemn his novel as racist would be delicious irony to Twain.
As for The Jungle, My Antonia and other period pieces, yes, people can argue that more modern literature can adequately replace these classics. However, today’s kids are amazingly ignorant of history. In addition to being excellent literature, they also provide a window into how people lived their day to day lives well as provide some structure to for followup history lessons. Otherwise, you end up with a college population like that in the following video that can’t answer who won the Civil War.