Every band can have off night. One of the WORST concerts I ever saw, Moody Blues, mid 70's last show of long tour. I thought they'd go out with big bang, instead went out with a snooze. I can imagine Mahavishnu would also greatly benefit from a sympathetic sound system, John's studio albums display a pretty 'crunchy' sound from his guitar, very biting at times. So, the best concerts ally good sound quality with performance intensity, involvement, this was far too rare in my big concert going days.
Speaking of live concerts and previous mention of Zappa, saw him three times in George Duke era, Frank was way underrated guitarist. Funniest thing, Frank was big chain smoker at the time, could swear he had cigarette going on all concert long non-stop, when it came time for solos, lit cig stashed up in headstock.
Since OP meant this for uncool leads, how bout another round of Free Bird. My recollection of that era was the constant rotation of the same songs on FM, that made even cool songs into uncool songs for me. Stairway to Heaven another example, could think of far more. I bet they continue to play the same overplayed songs on today's classic rock stations.