It depends. If the gaffe is really that noticeable that it pulls you out of your reverie, it is annoying. The occasional contrail in the sky probably not; Adidas shoes worn wit a toga, almost certainly. Current idiom used Victorian England, definitely.

Two series of books come to mind as poorly written:

John Jakes' Revolutionary War series of 35 years ago, which gave the reader (me anyway) no sense of time and place. I didn't even get through the first volume; I admit to liking the TV series of THE BASTARD slightly more, probably because of the visual aspect.

Another series under the umbrella title CHILDREN OF THE LION, covers the Book of Genesis, without any hint of religious impetus. Further, the events could have taken place yesterday, for all the description the authors (multiple authors writing as Peter Danielson)provide.

None of those books--and I think they had the same paperbck publisher--had the quality of writing as even TARZAN of the APES; Burroughs used a wonderfully large vocabulary, and wrote in complex sentences which keep the reader interested.