“Well, the Orthodox allow second and third marriages” is an argument made by some Catholics for loosening the Catholic Church’s teaching on marriage, which seems harsh and rigid and legalistic in comparison with Orthodoxy’s pastoral oikonomia. Orthodoxy does go farther than the Catholic Church teaches Scripture allows, but the rules aren’t nearly so lax as these advocates of liberalizing marriage claim. Nicola Bux, a professor of theology, explains in the always useful Chiesa that the Orthodox Church gives
a second opportunity in some particular cases (typically cases of ongoing adultery, but also by extension certain cases in which the marriage bond has become a pretense). A third marriage is also possible, although it is highly discouraged. Moreover, the possibility of entering a second marriage in the case of dissolution is granted only to the innocent spouse. Second and third marriages, unlike the first marriage, are celebrated among the Orthodox with a special rite, referred to as “penitential.”
This is not what Catholic advocates of changing the teaching on marriage want. I suppose they’d say that it’s the principle of oikonomia to which they’re really appealing, not Orthodoxy’s application of the principle in this case, but even if so, oikonomia does not justify the blanket approval of remarriage after divorce that they propose. Concessions require conditions and the conditions will necessarily be stringent and limit the number of people to whom the concession is made.