The Trinitarian Doctrine, which you seem to want to peg to Nicaea, which I don't, because I see the council as Christological, with Trinitarian ramifications, if you like, but certainly not the end of the story, and not providing a clear statement of Trinitarian Doctrine.
I'm not sure what you're understanding of Trinity is. As a working definition I'd say one ousia in three hypostases
You've used the Nicene homoousios, but you must acknowledge that term unleashed a whole subsequent array of disputes – the term was not agreed, and even its precise definition was disputed. Terms such as ousia and hypostasis were used, leading to confusion between Latin and Greek, as even in the Greek some treated them as synonymous and others as distinct classifications.
"The principal objection to the term homoousios had been its alleged Sabellian tendencies to eliminate the distinctions between Father and Son. But it was the Cappadocians who proposed an intermediate solution. The Father, the Son, and the Holy Spirit were homoousios (of the same essence) but they were not the same things, but three different hypostases. Here we formally meet the term hypostasis which means the actual reality of a given essence.
"To illustrate this term, we can return to our example of the term “tree.” The essence or ousia of tree is that which makes it a tree and not another thing. The hypostasis of “tree” is the concrete reality of this specific tree in my yard as a manifestation of tree essence common to all trees. The teaching of the Cappadocians was that there were three hypostases but one ousia which in English means roughly that there were three distinct entities but with one common nature. The Cappadocians had finessed Nicaea which had condemned the Arian belief that the Father and the Son were different hypostases, but using the term hypostasis in a different sense than Nicaea had. This remains essentially the Eastern Orthodox understanding of the Trinity to this day.
"The understanding necessarily lays a bit more emphasis on the distinction between the Father, the Son, and the Holy Spirit rather than on the oneness of God (which is emphasized more in western Catholic thinking) but nonetheless was a crucial breakthrough in the controversy. It for the first time provided language in which the threeness of of the one God could be spoken of and safeguarded."
Jesus Christ God, Man and Savior Week Six: God the Son at Nicaea and Constantinople (underlining mine).
I'm not sure what you're understanding of Trinity is. As a working definition I'd say one ousia in three hypostases
You've used the Nicene homoousios, but you must acknowledge that term unleashed a whole subsequent array of disputes – the term was not agreed, and even its precise definition was disputed. Terms such as ousia and hypostasis were used, leading to confusion between Latin and Greek, as even in the Greek some treated them as synonymous and others as distinct classifications.
"The principal objection to the term homoousios had been its alleged Sabellian tendencies to eliminate the distinctions between Father and Son. But it was the Cappadocians who proposed an intermediate solution. The Father, the Son, and the Holy Spirit were homoousios (of the same essence) but they were not the same things, but three different hypostases. Here we formally meet the term hypostasis which means the actual reality of a given essence.
"To illustrate this term, we can return to our example of the term “tree.” The essence or ousia of tree is that which makes it a tree and not another thing. The hypostasis of “tree” is the concrete reality of this specific tree in my yard as a manifestation of tree essence common to all trees. The teaching of the Cappadocians was that there were three hypostases but one ousia which in English means roughly that there were three distinct entities but with one common nature. The Cappadocians had finessed Nicaea which had condemned the Arian belief that the Father and the Son were different hypostases, but using the term hypostasis in a different sense than Nicaea had. This remains essentially the Eastern Orthodox understanding of the Trinity to this day.
"The understanding necessarily lays a bit more emphasis on the distinction between the Father, the Son, and the Holy Spirit rather than on the oneness of God (which is emphasized more in western Catholic thinking) but nonetheless was a crucial breakthrough in the controversy. It for the first time provided language in which the threeness of of the one God could be spoken of and safeguarded."
Jesus Christ God, Man and Savior Week Six: God the Son at Nicaea and Constantinople (underlining mine).