The first heresy was Gnosticism, followed by Arianism, then Monophysitism. Then some other heresies. Then Islam (which was a blend of Heresy, heretical Gnosticism & paganism). Then the Denial of the Filioque. But there is a simple solution to which all Catholics (both Roman-Rite & Eastern Catholics) AND Eastern Orthodox can agree: “Holy Spirit who proceeds from the Father ‘THROUGH’ the Son”. There, fixed for both sides (without making compromises), can we reunite now? When the Catholics & the Eastern Orthodoxs reunite, all of Christendom shall come together. Protestants & other heretics will cease to be, & will see the truth of Catholicism & join in full Communion. Christianity will be one as Christ prayed to the Father, & Islam & secularism will have no hold on us.
You really simplify the differences between the Orthodox and the Catholic Church. We will reunite when the Orthodox become Catholic. Until then the Orthodox Church is schismatic and should not be considered on equal grounds.