The difference is that Joseph Smith received direct divine intervention while translating the BOM. It was something he asked for, believed he could receive, & thus did receive.
The Church Fathers believed the Heavens were closed. There is no record of them asking for divine intervention in the compilation undoubtedly b/c they didn’t believe in it at the time. In fact the record rather indicates some testy battles as to what would be included & what was not. Same scenario for the Nicene Creed. No battles necessary when the Lord is telling you what to do.
I do believe in the Bible as expressed here several times. Do I believe everything is there? No. The evidence seems to back me up.
Pray tell, Reno. When was the last time you said: I do believe in the Doctrine & Covenants as expressed...Do I believe everything doctrinally expressed is there [from what was in the original]. No. The evidence backs me up.(?)