Your question could also be reversed to read: Why be Ukrainian Orthodox and not Ukrainian Catholic? However you phrase it, there is a tragic separation in the one Church of Kyiv. When the Great Schism divided the Eastern and Western Churches in 1054, the Kyivan Church remained in communion with Constantinople, following the spiritual, liturgical, canonical and theological tradition of Byzantine Orthodoxy. In 1596, due to political and church-related pressures which threatened its survival as a distinct Church, the Metropolitan of Kyiv and five of the other seven bishops of Ukraine, re-established communion with Rome through an agreement known as the Union of Brest, thus forming the Ukrainian Greek Catholic Church.
In my humble opinion, a Ukrainian Catholic is truly a Ukrainian Orthodox who is in full communion with the Pope of Rome. As such, we have the benefit of the Roman experience of Christianity while maintaining our Byzantine-Slavic heritage. On this point, our Patriarch Myroslav Ivan Lubachivsky (1984-2000) famously stated, “We are Orthodox in faith and Catholic in love.” We celebrate the same Holy Mysteries/Sacraments, we worship the same God in the celebration of the Divine Liturgy and other liturgical services.
Our human frailty, our sin, stands in the way of full communion with one another, so let us pray that we may be one as Jesus, the Son of God and the Father are one. Jesus said: “The glory that you have given me I have given them, so that they may be one, as we are one, I in them and you in me, that they may become completely one, so that the world may know that you have sent me and have loved them even as you have loved me” (John 17: 22-23).
Respectfully submitted by Fr. Julian Bilyj