(Expanding my comment a bit. Disclaimer: I'm not a soils scientist, just a guy who reads about gardening and related topics a lot.)
Pure compost would be nearly 100% organic matter. Soils have an inorganic component (minerals, rock particles, etc). You could build "rich soil" by mixing compost, sand, silt, clay, etc in the right proportions, depending on what kind of soil you want to build.
There are tons of different kinds of soils on earth, and they can be divided up in numerous ways. Sand vs Silt vs Clay (i.e. by particle size). Organic matter content (low vs high). For growing purposes, we often also talk about soil pH (acidic vs alkaline).
It's very much a possibility to "design" a soil that suits your needs. See my favorite recipe for potting soil, which mixes garden soil with sand to get the desired grain size (for drainage purposes) and then adds compost (for plant nutrients and organic matter), lime (to raise pH), and mineral fertilizers (plant nutrients).
You could do the same thing on a large scale by having three dump trucks swing by your house and deliver one load each of composted manure, sand, and topsoil(*). Add a few bags of lime and some mineral fertilizers and then all you'll need is a bulldozer to mix it and spread it around your lawn.
(*) "Topsoil" is kind of begging the question, I guess. You could get really specific and order up precise quantities of sand/silt/clay in the desired proportions. When I'm mixing potting soil, I just go by how it feels in my hands so that it's the "right" consistency.