When reading old books sometimes the language might feel old. The language evolves constantly, so that's not s surprise. But sometimes it accidentally makes the reading experience better.
When reading either fantasy or historical fiction the old language actually makes the experience feel more authentic. Of course many modern authors use this method for that exact effect. But I have read older books where the case definitely wasn't this.
It gets more interesting when reading science fiction. Old language in a post modern world just sounds weird. There might be technological marvels those visionaries called by completely different name as we know them today. On the other hand, many of our modern technology has gotten their names from those old authors imagining things they never believed they wouldn't see within their own lifetime.
I'm sure many modern day masterpieces of sci-fi will sound as odd and out of time for the future generations. As I grow older I have already encountered this with books actually written during my lifetime. Did we really speak like that back then?