"Since the end of world War I, war literature has unquestionably been anti-war in its aims." -Robert Fay
"Instead of striving for neutrality, the first step to truly affecting game design is to realize that nothing is neutral: what we see as a lack of bias is our own blindness to the circumstances we live within." -Elizabeth Sampat, Empathy Engines
Games that have themes can never be viewed as merely systems. Themes, settings, characters, or stories: these elements give systems meaning. Even if you are pasting a theme onto an abstract (or combinatorial) game. A game that uses flower tokens carries a different message than a game with grenade tokens, even if that message is only that you believe that flower games will sell better to your intended audience. Giving a game a certain theme is a statement of cultural value.
Making a great deal of games about colonialism from the colonizers' perspective is also a statement of cultural value (or at least perceived cultural value). Games, like history itself, contain the biases and perspectives of those telling the stories. Striving to make games without a perspective beyond "the facts" is impossible: games are abstractions and what gets abstracted (or left out entirely) is up to the editorial discretion of the designer. What is included and what is left out reveals the designer's perspective.
But beyond acknowledging our biases, I believe designers need to embrace the concept that all themes have subtext. Embracing subtext means embracing layers of meaning. Depth of meaning is a key element when creating quality art. War novels are not merely about war; they are about presenting objections to war by showing the horrors of war.
Leveraging meaning in game themes can produce powerful experiences. Think about the difference between The Grizzled and Memoir '44. The Grizzled addresses the impact of war, not merely abstracted events such as unit deployment. Addressing impact and telling more nuanced stories are a fairly straightforward ways to add meaning, because showing the human cost of events invites your audience to empathize with the characters represented in the story.
However, realism is not the only way to add meaning to a theme. Spirit Island is a game with a complex mechanical system and rich thematic setting that repudiates the idea that a game needs to be historical in order to have anything to say about history. Spirit Island is historical fantasy in genre, but the subtext is a repudiation of (historical) colonialism and the depiction of colonialism in board games. Speculative fiction and even fantasy can contain metaphors for the real world. A setting does not have to be factual to contain truth. Sometimes, a setting isn't even "about" what it is about. The Crucible is a play set during the Salem witch trials but is about McCarthyism. Into the Woods is a fairytale musical about the AIDS epidemic. Subtext takes fairy tale characters and tells us deeper truths: even when people are dying indiscriminately, "No one is alone."
Game themes span the spectrum of depths of meaning. Designers should be intentional about the meaning they infuse into their games, even if that meaning is fairly surface level. Designers should be aware that they can add deeper meaning to their games, but even if they do not, their biases will still underpin the game world. Lastly, designers can create empathy in players by addressing the human impact of a theme, whether that theme is based in realism or falls into the fantasy genre.