It can be done, and done well, but it isn't easy. Sound must be very carefully controlled, focused only on listeners with as little as possible spilling onto walls and ceilings. This takes the right type of loudspeakers in the right place and very carefully aimed. Loudspeakers designed for bar bands or for touring sound are rarely the right choice here. Second, the place of sound and amplification has become much more central to praise and worship.
Music is used to inspire, to lift the spirit, and to bring the unchurched into the fold.
Choirs which used to sing with only a piano or organ are now accompanied by a contemporary band. The sound system must be able to make the choir much louder to balance with drums and electronic instruments, and the various musicians must be able to hear each other well to play together. Again, careful control of the sound is key if this is to be accomplished without feedback. Acoustic design of the worship space is fundamentally important to both of these concerns, and many churches are designed with no competent acoustic advice. Often, there is so much reverberation in a church that the praise band has turned to mush before the sound system is even turned on.