I hear you. By and large, I'm usually more patient with the Christmas service, because the MD usually gets people from the congregation to come up and sing some pieces and many of those people are modest talents at best. Had a lady who was Haitian sing "O Holy Night" in English and French, which was cool. Her timing was off at points, but it was a very beautiful piece and easy to jump a beat/add one in a couple spots to help her out.
But we had two sisters come up at rehearsal, with just the guitar tab for the Transyberian Orchestra's version of "Carol of the Bells" and expect us to play it. After one run through, it was apparent that it wasn't going to work but they wanted to go through it again at the end of the rehearsal. It was better, but still nowhere near where it needed to be. Still, they insisted to the MD that it was going to be fine for services last night. Thankfully, as I walked in yesterday, I was told that they decided on a more traditional piece that they would play as a flute duet. Went off much better.