There is an oft repeated idea that you can tell what a game wants you to do based on where it puts the weight of its rules (page count wise). I am not so sure.
Let's take the obvious example: D&D (nearly any edition, but post TSR editions especially). The vast majority of rules that exist in the game are focused on the combat system. Note that when I say "rules" here I mean everything from actual gameplay mechanics, to spells, class abilities, monsters, items, etc... I don't think this is a controversial statement.
That said, I do not necessarily think that translates to the intended focus of play for D&D is combat. It is of course important, but it is one of 3 pillars that are generally considered to be equal, as far as play focus goes (from the design intent standpoint). Rather, combat requires more detail in D&D (and other traditional games) because of what it is trying to accomplish in the world of the fiction. The social and exploration pillars could be just as detailed as combat (and in some games they are) but in D&D the GM is supposed to do the work that those systems might otherwise do in the social and exploration pillars, and let the rules make combat "fair." There are lots of reasons this might be the case -- and we can talk about that -- but the main point is that just because there are a lot more rules, that doesn't mean that the things the PCs are supposed to be doing in the world is fighting in the substantially same ratio of rules volume/page count.
Note that this is slightly different than the amount of time spent at the table. Crunchy combat systems can certainly eat up more actual play time, but that still isn't that same thing as saying "lots of combat rules necessitates lots of combat in the story."