I can never tell the difference between supposedly good audio and the equivalent of two cans connected with a string. Dunno, maybe I'm lacking the audiophile chromosome or something.
This one has a good example of bad vocal audio (at 1:00): https://youtu.be/-PLMiA18tBc?t=60
A mediocre mic placed 3-6" from the mouth is going to almost always sound better than any price of mic placed 5' away, except in sound treated studios with excellent technique and strong post-processing.
Have you seen the movie This Is Spinal Tap? Good scene on this "common knowledge":
i'm not an audiophile either, but some videos really had audio that was terrible enough to make me quit that.
examples: some buzzing in the background, high-pitched noise in one of the channels, or audio in mono (you only hear the person talking from the right ear, for example).