I don't want to make it reductionist at all, you're right.
A more enlightened view of compensation, if you need a more general economic way of looking at it, is: "In a world where most of economic value exists in human relationships or in computation, compensation is more about (1) how accounting reflects that economic reality, and (2) how well the compensated individual extracts accounting value from whatever big picture the accountants came up with."
In that sense, unions are exactly the remedy, because they negotiate how these employees are paid relative to the accounting value of their business.
It's all accounting! I can't emphasize this enough--you can pay the employees 2x as much, or 10x as much, or 1/2x as much, and Fortnite will be EXACTLY as fun as it is now. That's what people are outraged about.
This is totally unlike another notoriously unionized industry, autos, where a lot of the value is tied up in really objective, physical stuff like gas mileage or maintenance. Most of the economic value of Fortnite is in the experiences it makes between friends and the computer code consistently delivering that experience, whether on your phone or in the servers.
Supply/demand as the framework is kind of a stupid point of view. We can't listen to too many finance/economics people, especially the rich ones we actually hear from as opposed to the poor ones who may be right but whom we don't give a shit about. The rich ones aren't in the ground level of humanity anymore. That's what the perspective on HN is really about: sorting out which rich person you agree with.
But if you want to do the right thing, you unionize because it will get these people paid better and feel happier at basically no economic cost.