It didn't matter. Their hearts sang louder than their voices -- and far more in tune to the rest of us parishioners than a paid and technically-proficient choir could ever do.
Actually, choirs get good not by making noise but by learning to sing as clearly and quietly as possible. Think Gregorian chant. Simple music sung quietly and beautifully is within reach of any amateur choir.
Churches that spend a lot on singers make me sick. That's why I quit my old choir.