Compressors in the hands of people that don't know how to use them are about the best way to kill sound. I've been in churches where that is exactly what happens. A sound volunteer who doesn't know what they are doing, and has compression set all wrong can make it sound worse than if there was...
One of the secrets to getting midi orchestral instruments to sound even half realistic in my experience is to use well chosen reverbs (and possibly delays too) to create a sense of space. Using more than one reverb, and panning them a bit can help too. Varying the depth of the reverb for...