"One of my big problems with The Alienist was the anachronistic "signaling" to the modern reader.
Someone who rides in a horse-drawn carriage over cobblestone streets all the time would not have an internal monlogue that went into great detail about it feels to ride a horse-drawn carriage over cobblestone streets.When I am in the back of taxi driving under sodium-vapor lights, my internal monologue doesn't go into great detail about sodium-vapor lights."
- in which he's put his finger on the basic flaw in historical fiction (or perhaps fiction); we all have an enormous amount of embedded knowledge that we don't call to conscious thought but which governs the conclusions we draw from our conscious thought, and the author can either make them explicit (as they would not have been) or not (leaving everybody's motivations inexplicable). I've seen it described as the "your brother, the cardinal" problem, as in "Here comes your brother, the cardinal." -- the villain doesn't have to be told that his brother's a cardinal, but we do.
And the problem with making the past understandable is that it isn't. It's another country, they do things differently there, only Eco has made any fist at all of embodying this. Possibly Alfred Duggan, in the opposite way. Possibly Jonathan Strange and Mr. Norrell.
And asking for a sympathetic hero only doubles the scope for error. It's virtually impossible for any person born before, say, 1945 to be painted with their true opinions and not be unsympathetic. In Gladiator, say, we were expected to believe that a Roman general would get all choked up about having his wife and son killed, when (a) this was Rome, alliances shifted all the time and you couldn't afford to hold grudges simply because a few of your relatives had been topped, and (b) as a Roman general, he was in the business of bringing other generals' wives and sons back to Rome to ride in triumphs and then be killed.
Moving to reality, Caesar was responsible for the deaths of about a million Gauls (his figure)and gets played as a loveable old softy (Rex Harrison) or a Victorian statesman.
There's no point in inviting people into history by making it more like today. That's like getting children to like the taste of Grange Hermitage by stirring in chocolate syrup.