Wisden, I am just a lowly PPL/IR in progress guy. I make a mistake every time I fly. Luckily, my mistakes so far have been relatively trivial (overshooting a frequency when tuning a radio, giving out a wrong call sign by transposing numbers, reading something back incorrectly in a clearance, taxiing a bit off the "centrelines", being a bit off the centreline when I land etc). I try to accumulate knowledge about mistakes and not make them again but there is unfortunately some repetition.
I fully expect to make a big mistake at least once in the pursuit of my hobby. I really hope that it doesn't kill me. If it does, it won't be because I am cavalier in my approach to flying.
Professional pilots are also human and they will also make mistakes. Their mistakes will be less frequent and less consequential than mine as they are professionals and I am only an amateur but they will still make them.
Finally, I think that BA, KAL, AF and SWA pilots (as well as everyone else) will make mistakes in roughly similar proportions per 100,000 hours flown no matter what equipment they fly. There is an amount of randomness to the consequences of those mistakes. The incident in Joburg might be a bit of "catch up" in the randomness of consequences.