Of course, writing historicals puts a new and different twist on dialogue. Some words and phrases have changed meaning over the years. Having my 1920’s heroine say she wants someone to make love to her means something much different to her than to a reader in the 21st century.
But, there are some things writers get hung up on, though it may not be historically accurate. People have been using contractions for hundreds of years, but, for some reason, it’s in people’s heads that it’s more historically accurate for them to say ‘do not’ as opposed to ‘don’t’. Why force a reader to drag themselves through boxy, awkward sentences? And how about writing, say, an ancient Egyptian story? Since you’re obviously not going to write the manuscript in your character’s native language, you have the freedom to let them speak in plain English. Much easier to write and to read than complicated attempts to make them sound Egyptian. Especially since those attempts many times turn out to sound suspiciously like Hadji from Johnny Quest.
To keep your reader firmly based in your time period, a smattering of native words, references to items and places identified with your era/place and acknowledging political, ethical and community traditions will take you much farther than using stilted English ever will.