Lisa Hirsch writes about the negative effects of amplification in the Berkeley Rep. I experienced a similar amplified performance when I took my daughter to the Indianapolis Symphony Orchestra's Yuletide Concert. I wasn't bothered by the amplification of the singers, but the orchestra seemed very flat in timbre, dynamics, and emotion. Hilbert Circle Theater is already a problematic performance space, as it was originally designed to be a movie theater rather than an orchestral hall. The auditorium doesn't have enough volume for decent reverberation time, so they had to design electronic "cheats" to give the proper acoustic signature. They turn off these cheats when doing their pops concerts, replacing them with a blanket amplification. The brass, seated way up by the organ pipes, have none of the shock-n-awe that they normally produce, because the amplification normalizes the loudness of every section. Thus the brass is as loud as the strings, or even the bassoons fer chrissakes!
I don't think amplification automatically creates a bad performance experience. But I do think very few sound engineers have the time or knowledge to accurately capture the nuances of a full orchestra.