This is frequently stated but when it gets down to brass tacks seems to be somewhat exaggerated as the source of all archaisms from the POV of later readers. From what I can tell, while some things (like second person pronoun use) where archaic at the time of writing (and egregiously bad choice of archaism because they created distinctions not made into the source material by using a distinction no longer currently in use in English, either), many others were things that were in transition at the time of writing and which didn't reflect later (and also, in some cases, earlier) common usage (thereof to avoid possessive pronouns as gendered ones relating to inanimate objects were on the way out, but “its” was still not firmly caught on).