Good topic. I say it is the sound board person. I attended an outdoor concert a couple of years ago. Cheap Trick, Heart, Joan Jett. Sat dead center about 20 rows back. Cheap Trick was a total mess--could hear NO vocals, the guitars were a smear, and the bass was non musical, only gut-thumping. Then came Joan. PERFECT sound mix, dynamic range, was like listening to the recordings live. Then came Heart, one of my fav bands. Again, a total mess--vocals, which are obviously their strong suit, were not intelligible, the band mix was terrible, and there was no definition of the instruments, just a wall of loud noise.
SAME PA system, SAME board, terrible mixing.
Saw Steve Miller band a couple of years ago indoors. SUPERB sound.
Went to an indoor concert not long after for a famous female vocalist. HORRIBLE sound, no vocals that could be distinguished, and a terrible mix of the band.
I would agree that the sound board person is at fault. I refuse to attend any more live concerts, and I have seen almost everyone since 1962--I keep the ticket stubs and remember them. Good ones--Beatles outdoors, Stones both inside and out, Hendrix indoors twice, etc,. etc., etc. Even the Dick Clark Caravan of stars outdoors in Raleigh in 1964 was excellent with over a dozen DIFFERENT acts including Gene Pitney and the Supremes--totally different sounds. Great sound from equipment that was NOT digital or advanced.