I completely agree with you. I believe the entire dogma of SHAAN-E-NUZOOL was concocted to divert Muslims from the Qur'an to Hadith.
I am not aware of a single verse in the Qur'an that requires external sources for our understanding.
"Light does not need a candle to reveal itself." (Allama G.A.P. quoting Allama Iqbal).