The Orthodox actually did missionize Rus extensively even *after* the schism hardened. The mission began around the time of the schism, but didn't end then -- instead it extended for some time. And, of course, thereafter the Russians spread Orthodoxy eastward with them across North Asia and into Alaska, notably translating the scriptures and services into several Aleutian languages. Today, Orthodoxy is still the largest religious affiliation among the Alaskan Aleuts -- see www.alaskanchurch.org
. Orthodox Churches are also scattered across North Asia, inlcuding in Japan, where there is a small but significant community -- but all of us Christians know that with a few exceptions East Asia has not generally been fertile ground for mission.
I have heard this argument raised by more than one of my Roman Catholic friends, and the reality of the matter is that the Latin Church spread the way it did because the Western European countries that were "discovering" (read: Taking Over) the remainder of the planet were often Catholic -- the Spanish, who colonized Latin America, California and the Philippines, the French and Belgians who colonized much of central Africa, etc. Places where the Protestants colonized, like the USA, have remained mostly Protestant, with inroads coming through immigration of Catholics, not really through mission. During the "Age of Discovery", the Orthodox world was either (1) enslaved by the Ottoman Empire or (2) living under the relatively backward and isolated Tsarist Russian Empire. When the Russians began to catch up a bit, they did missionize the places where their empire took them ... but there was no place for the Greeks, the Balkan Slavs or the Middle Eastern Orthodox to missionize, and no means to do it. That's why things have shaken out the way they have ... not because of some self-satisfied smugness that some RCs would accuse of Orthodoxy, but rather simple brass-tacks history and the fact that the RC enjoyed the spsonsorship of powerful, expansionist regimes during the "Age of Discovery" and utilized this well to expand the Catholic Church substantially beyond its Western European roots.
Today, we are faced with a different missionary situation altogether. Orthodoxy, right now, is primarily engaged with re-missionizing itself. The Gospel needs to be brought to people throughout the Orthodox world who are suffering the effects of living under a militant atheist regime for many years -- that's simply priority number one right now, and a LOT of effort is going into it. In spite of that, however, there is quite a lot of quite missionary work going on throughout the world -- we do not seek, for the most part, to poach other Christians, but our door is open, and our open doors have attracted a good many visitors in North America and Western Europe in the last 10-20 years, a good many of whom have ended up joining our ranks. In a sense, many of us are convinced that this kind of "open door mission" is the most effective way for Orthodoxy to missionize in our contemporary society. (And, of course, as some former Eastern Catholic-tiurned-Orthodox priests have mentioned to me, the revitalization of the Eastern Catholic Churches has proven to be of great benefit to Orthodoxy as a missionary venue -- not because we poach Eastern Catholics, but rather because many Latin Catholics, like Byzantino, first approach Orthodoxy through the relatively safe venue of Eastern Catholicism -- after all "it's still Catholic" -- and fine their way eventually to the Orthodox Church -- one Orthodox priest friend of mine once admonished me not to be too critical ofthe Eastern Catholics, saying "If there weren't any Eastern Catholic churches around, do you think you'd be Orthodox right now?") Nevertheless, one would hope that when Orthodoxy gets back on its feet more fully in a few decades time we will also see increased Orthdodox efforts to bring the Gospel to those places on Earth where Christianity in general hasn't been very succesful -- such as East and (much of) Southeast Asia, and parts of sub-saharan Africa.