The Last Supper is in reality Christ's very sacrifice on the cross, they cannot be separated. And as Jesus said, if you do not drink his blood and eat his flesh, you have no life in you.
The music and the behavior of the priest are secondary.
When the people in the church use your presence as an opportunity to sell sweetly-worded destruction to the community, voting with your feet can be the most God-afirming move you can make.