Hi! Absolutely agree. And I think two things are the main ones that lead you to make that decision, at least based on the saga I'm writing.
1. You write the story you want to read.
The one you have visualized all these years while walking down the street and you have felt it as real and detailed as a movie. Well your brain, your personal blender where all the things you see or read are mixed, is not thinking about gender classifications or thematic censorship. It gives you a product according to your own personality, and even though you could manipulate that visualization already turned into a novel (with your mind set to a Ya, for example), it is not always possible, or you realize that it will lose its power or original purity, and something in your head will not stop ringing like a bell telling you that you are corrupting something that was unique and valuable. Or that you are selling you to the market.
Exactly the same thing happens with music.
Also, unconsciously everything you can write has a framework of possibilities previously determined by what Harold Bloom calls "Anatomy of Influence". There are writers that you like more than others; then it is inevitable that some of that will be reflected in your stories. And, BTW, when it comes to studying a subject, the Civil War, for example, one also searches for books even by authors that one does not know. Or you see series like "The Blue & The Gray", "North & South" and, of course, "God & Generals".
There are also gender issues. Eroticism, for example. On the one hand, in sci-fi novels it has a rather naive treatment while Fantasy far surpasses it. Still, self-imposing a PG puts automatic restrictions on you.
Although it is obvious that at the time of the Secession men were much more courteous and delicate and people in general more naive. Ex: Picnic civilians trying to get a good panoramic view at the actions in the Battle of Bull Run and when it all goes to hell they running away like rabbits.
2. The conceptual and ideological framework of a story defines its target audience.
As you say, developing all those concepts (racism, colonial expansion, warfare going industrial) a Ya reader will surely understand them, but most likely, they will get bored. In the same way, a magic flint weapon will interest the Ya only as long as they see it firing.
Instead, an adult will most likely want to know how that weapon works, and he will even be disappointed if he does not see any explanation, even minimal.
In fact only a few details are needed.
He does not need to know that the Argall spark arrester (it just occurred to me, you can use it if you wish) that makes the weapon work comes from a mineral that is only found in an African mine, but that had to go into jungles to obtain it , fight with wild beasts and cannibal tribes and also nobody knew where that mine was, so they first had to find a priest of the order of, etc, because he was the only one who knew where the damned mine was, etc, etc. No. All you have to do is tell what mineral the mysterious and magical Argall spark is made of.
Suspension of disbelief doesn't take much theory to rule out the Deux ex Machina. The reader will see that there is a certain material, metal or alloy that he did not know and will accept that it has some importance in history. And then, based on that, he will continue to accept and consider as logical all the subsequent conflicts that may arise derived from the importance of these materials. What do I know, these can be:
» Contraband of Argall.
» Kidnapping of mystic alchemist engineers who are experts in arcane flow.
» The desertion or murder of an important scientist or mystic.
» Derailment of a federal train carrying valuable pipes and condensers whose unique utility in the world was that they could resist the dangerous instability derived from the industrial process to manufacture certain ammunition.
» The unexpected flight of slaves who were to be assigned to these dangerous industrial tasks. As you say, if the "magic use can and does cause long term health problems", this also produces a conflict of a moral nature. So perhaps it is necessary to resort to people who have no chance to question anything or claim their rights, forced to work on something that they will lead to death or sure deformation. In other words, cheap labor.
Also, going back to those concepts (racism, colonial expansion, warfare going industrial), contrary to young readers, an adult will always read willingly a reasonable development of all that. He wants to know what the narrator of your story thinks about the various issues behind a certain conflict. And history will seem weak or insufficient if he doesn't see it.