"A child who reads will be an adult who thinks."
Whoever first said these words uttered one of the greatest educational truths ever spoken.
The fact is that, if a person can read well, he can learn about nearly anything else in the world, as needed. There are, of course, other wonderful ways to learn - i.e., learning by doing (hands-on, project-based activities) and learning by direct experience (i.e., travel). But most of us won't travel as extensively as we'd perhaps like to and even many hands-on projects require some reading as well. Thus, being able to read well enough to enjoy doing so is an educational hallmark.
As I've pondered this concept over the years - while concurrently seeing myriad homeschool moms fret over what subjects to cover with their kids and even thinking about that for my own children - I've come to a strong conviction about the foundation of our home education endeavors: If my kids can read well (which means that they'll be "thinkers" by default), communicate clearly (orally and in writing), and competently manage computational math (not necessarily "higher math," depending on the child), all the rest is gravy.
In other words, those "basic" skills (the old-fashioned "3-Rs") really do provide the foundation for all other learning. It's not that we shouldn't address other content areas like history, science, the arts, etc. In fact, I believe we do well to find engaging ways to expose our kids to an overview of those various "subjects" before they reach adolescence in order to build mental "hooks" on which they can hang all that they'll learn through the rest of their lives. And then in adolescence, we should endeavor to maximize the development of the unique gifts and abilities we begin to see in each child, diligently working through a wholly customized plan for each one (i.e., there should be no such thing as a "standardized curriculum" - where every young person has to learn all the same content) in order to prepare them all to confidently launch into adulthood. But when it comes right down to it, once a child has learned to read well - or, if true reading disabilities exist, to employ very helpful technology such as audiobooks - his educational toolbox is ready to tackle any cognitive endeavor he seeks to pursue for the rest of his life.
In reality, if we give our kids "only" the 3Rs - a rock-solid foundation in readin', (w)ritin' and 'rithmetic! - and then commit to a fully personalized plan for other content areas (purposing to eliminate every vestige of "filler," material we think kids should learn only because "everyone does," and busywork), we have given our kids everything they truly need to engage well in any life endeavor each might choose to pursue.
Nurture kids into becoming strong readers - when the time is right for each one! - and everything else in the world will be open to them.