Was your sunset picture, with birds flying by, subjected to post-processing? If there was, then what were the controls used?.
It is an extremely good picture, though some might call it "dramatic". Sometimes it so happens that the play of light makes dramatic scenes . One possible reason why the picture was rejected, is that people are getting inured to HDR processing. This might be knocking out pictures which are naturally dramatic without looking like something extra-terrestrial.
Best wishes.