While there has been progress in reconcliation of the OOCs with both the EOC and CC, in particular in differentiating mono- versus miaphystism, the OO still do no accept Chalcedon.
Yet they still remain far closer to Orthodoxy than the Catholic Church
This is not seen as a church dividing issue by theologians and scholars. The key point, in agreement, is that the Father is the origin of the Spirit
I do agree with you that both Churches do agree that the Father is the Holy Spirit’s origin; however, Catholics go beyond that which was revealed in the Bible & in Ecumenical Council and claim that the Holy Spirit has 2 eternal sources of origin, the Father and the Son as if from a single spiration. But it truly is a significant dividing issue. Many mainstream Orthodox Christians (laity), authors, theologians, etc. has spoken & written about whether or not Catholics even worship the same God based on how significatly different the belief about the Trinity is.
Doctrine of course develops in Orthodoxy as well. The ecumenical councils clarified teachings - they taught “more clearly” on the Trinity, on the divinity of Christ, on the Theotokos, etc. There is no reason to think that Aquinas would now have trouble with the IC than Chysostom would with the sinless of the Theotokos.
**Orthodox do Not and never have believed or taught Development of Doctrine.
RE: Catholic St. Thomas Aquinas based on his own detailed writings against the IC, I can’t come to your conclusion that all of the sudden he’d change his mind.**
CC theology uses the term created grace in considering the impact of grace within creatures.
**This sentence doesn’t make sense to me. You’re saying that the Catholic Church teaches that Grace is created because it has an impact on humans? If so, we believe the exact opposite.
Nothing created deify humanity, only God Himself can do deify us. And He does that through a very real sharing of Himself, His Divine Energies also known as Uncreated Grace.**