Part of the reason for this shitshow is that there is no competition over who sets exams. All state schools in Scotland, and the private ones which do Highers (most of them) must use the SQA. It's been that way since at least the 80s when I was doing my exams, probably earlier. No accountability. No incentive to do things better as you have guaranteed "customers" each year.
So why don't the Scottish Government open things up a bit? Either allow someone else to set up, for example,, The Caledonian Exam Board? Same curriculum, different exams. Schools opt for one or the other. SQA continues to do a shit job, they lose customers. And money. And Swinney's brother and Nicola's school mate are out on their ears.
Or even it doesn't have to be that complicated. They allow AQA, or EdExcel, or whatever other exam boards are already up and running in other parts of the UK to start setting exams in Scotland too.
When you have one organisation operating a monopoly there is NO incentive to improve. Shake things up a bit. Give headteachers the power to decide what's best for their schools and students .