The burden of proof rests on the accuser. The first problem you would run into is that the opposite of “orthodox” isn’t “progressive”; it’s (literally) heterodox. Orthodoxy and heterodoxy have reference to what’s been defined by the Church on the basis of Scripture, which, as the Word of God, contains all things necessary to salvation. And what are those ‘necessary things’? - The Articles of the ecumenical Creeds. The Apostles’ Creed doesn’t mention belief in a literal Adam (or a literal Satan, as C.S. Lewis once noted), as necessary to salvation. Nor does the Nicene. Remember, it was the allegorizing (and Origenist) Alexandrians, like Athanasius and Cyril, who landed on the right side of orthodoxy during the Trinitarian and Christological controversies, not the overly literal Antiochenes, like Theodoret and Nestorius. Nor does the Athanasian. They do mention things like belief in God, the Trinity, the Incarnation, the virginal conception and birth, the crucifixion, descent, resurrection, and ascension of Christ, his unity of Person and duality of natures, the last judgment, the communion of saints, etc. Each and all of these things are required for belief. Now, if a Christian questions the historicity of figures like Adam, or Moses, which article of the Creeds has he violated? In what way is such a person truly ‘heterodox’?