Well said Cary. My example has always been historical novels. I've read many a novel set in, for example, WWII, where fictional characters are set in real events. It's no trouble at all for these authors to write within the confines of established events that actually happened without altering the event in the least, and fit their own characters and adventures within that framework.
Nobody has ever inserted Me-262 jets into the Battle of Britain because "modern audiences might think Bf-109Es look too old fashioned, and no one ever specifically stated they DIDn't exist then!"
A good writer can use an existing history as a viable framework without needing to alter it or ignore it. Heck, in "The Buried Age," Christopher used almost everything ever mentioned on screen and didn't contradict a single thing! Hell of a feat!
Lazy writers ignore or rewrite history because it's too much mental work for them to bother or care. (and I DON'T mean the Turtledove method, which requirea an intimate knowledge of history in order to experimantally rewrite it).