Our pastor's wife intentionally and specifically chooses songs to play for background music during meet and greet that are the same songs we will be singing on stage later, so people will already know them or at least have heard them before by the time we sing them.
About the mix being bad, that could be because the sound man is half deaf. Been there.
The dichotomy of overproduced, pre-packaged worship and good sermons is striking. Usually both will be bland or both will be good, the worship and the sermons. The only cause I can think of is maybe they are overseen by completely different groups of people, with different overarching aims for the service.
One nitpick: The author complained multiple times about singing which goes beyond the lowest common denominator vocal range. Sometimes a song is not sung at church for everybody to sing along with, but for a solo to sing. Songs that go above and below what everybody can sing is not necessarily a bad thing.
Final thought: no matter what the cause, the result is the same. If you don't like it, find a different church.