Then we agree on everything! :)
Obviously that is not the case.
With the Mormons, they teach in a way not in accordance with the Faith passed on through time from the Apostles. They are heretics... it's that simple.
The problem is in who gets to determine the content of the Faith. If there is no single head who can pass final judgments on disputed points of Faith, i.e., if there is no universal teacher who has universal jurisdiction over the Church, then a single Faith that is continuous through time cannot be assured with moral confidence. There must be an institutional unity for there to be a confessional unity. The Orthodox have no mechanism for determining the content of the Faith except an empty appeal to Tradition, but when they disagree amongst themselves there is no recourse for them. They thus are derailed into a faith that is re-interpreted by them in novel ways as new difficulties arise. Who amongst them could make any final decision and so unite them ? Each bishop is at an impasse.
As such, the Orthodox are uniquely subject to fideism and cultural inertia, since they cannot appeal to any systematic and universal rule of Faith. They cannot develop solutions to explain the metaphysical ramifications of this or that doctrine, such as the Church Fathers under the guidance of the Roman See did. As such, the Orthodox faith is irrational, since it is not ultimately something that can be examined and explained by reason guided by and grounded in Revelation. On the contrary, it becomes not a reasonable but merely a ceremonial religion that justifies itself (in a circular manner) but cannot be justified to others by appealing to reason. One instead becomes part of some Orthodox camp, rather than a universal Church. It follows, then, that Eastern schismatic churches would invent such novel absurdities as allowing divorce and artificial birth control in order to better follow "the heart." No authority amongst them or rational discourse could gainsay the appeal of so-and-so's heart. Here is an argument based purely on an aestheticised spirituality and nothing else; faith, then, becomes the opponent of reason in the Orthodox... "
system." There is no connection to the Faith and practice of the Apostles there.
We're not talking about a private experience of Faith.
Not as private as the Mormons, but private nonetheless, since ultimately the numerous Orthodox confessions are not based on a Faith assured by the universal Church. They are based on something beyond the grasp of public teaching and reason and that cannot be explained in its origin or its dynamics. It is located somehow in the liturgy, which is explained by the bishops, who are beholden to the liturgy, but none of whom can make their doctrinal judgments to be obeyed. In the Orthodox scheme, a truly catholic Church is impossible. There is no question of inherent credibility, one just take's another's word for it, full stop. Where the authority behind his word originates is anybody's guess.
It's one that's lived and experienced in the context of living Sacred Tradition extending right back to the Apostles, in a community of believers.
Says who ? The point of divergence is that you seem to be advancing a type of fideism that rejects metaphysical arguments, systematic theology, and a comprehensive legal corpus. There is none amongst your schismatic sect that can demonstrate a clear connection to the Apostles in Faith. The marks of the Church are absent from your groups. These things can only be found in the Catholic Church founded on St Peter.