This was a great piece of science fiction. The stuff about loosing words and how we as listeners got some context via the ship's computer was nicely integrated.
Minor nitpick as an armchair anthropologist: While a hunter-gatherer society certainly does not have the disposable woman/manpower to built universities and write literature, that does not mean that their language is simpler than ours. In fact, isolated/ "small" languages are often more complex than the big ones, like English. What could of course lead to a decline of the language is isolation, like the protagonist. Of course, meanings of words or knowledge about stuff from a more advanced past might also fade. But language in itself would still remain vibrant and complex as long as there is any group of people.