I just sang unamplified in a big old church. Oh bliss! They had to build them with the acoustics in mind in the days when this one was designed.
I do always make a point of thanking the sound crew from the stage when I do have to use amplification, and it's been well done. Usually it is, in my experience, and I'm not famous or well known. I believe that "loudness" is maybe usually under the control of the performer. I do understand the problem of how to be heard by some people and be background for others. Doesn't work generally but you can't tell that to a restaurant owner. Cheers and thanks and Koala stamps many times over for the sound crews.