1. "I'm not doing a good enough job."
2. "I'm playing to the wrong audience."
Sometimes there is the 3rd reason - the church has run out of money.
Often "not good enough" has nothing to do with the number of mistakes we make or what kind of music we play but everything to do with what kind of connection we have with our audience (congregation and clergy).
Increase the connection and maybe you'll eliminate the second reason as well.