One of the biggest trends in game design is marrying a specific ruleset to a specific world, so that if you enjoy that ruleset and advertise that you play using that ruleset, people have an immediate understanding that you’re playing in the world the ruleset is designed for. Even rules that don’t try to force that relationship usually can’t escape some kind of intrinsic tie (like the names of deities, for example).
The danger of this approach, the way we saw it, is that it either reduces the rate of adoption for a ruleset or it makes adopting the rules extra work for the GM who would like to use them for a world other than the one they were designed for. This was highlighted to us when conversing with several local GMs who like certain rulesets, but whose players had no interest in the worlds the rules were designed for. Some of the GMs started working to modify the rules to fit with worlds of their own design (or even worlds built around other, different rules). Others decided that even though they really liked the rules, they would never find players willing to try the (sometimes radical) game worlds, and gave up on the rules.
Our approach to developing the Infinite Earths rules is to divorce them from story, and from setting, entirely. The rules must be free! From all constraints, so that if you use one of our worlds, you can use the rules as written. If you use one of yours, you can use the rules as written. Or if you want to use someone else’s world entirely–our goal is to make the rules as broadly useful as possible, while still providing the pinpoint adjudication that makes rules useful in the first place.
That said, our introductory ruleset will be classic western Fantasy, with expansion into a Space Opera ruleset later. As we take many of our design cues from fiction, and not from classic game staples, we’ll expand outward as we go. Not with splat books or rules that pile on, but with rules designed to encapsulate that particular genre.