My take on it as a retired PTC...
Labour brought in the disastrous CfE. The SNP ran with it because of sunk costs.
Teachers were supposedly consulted - but our protestations were ignored. I actually wrote to my MSP. She passed my complaints to Mike Russell. He very helpfully wrote back to me to say that teachers had been consulted.
The coursework in Nat 5 and Higher has led to a great deal of cheating and contributes to the mindset where many pupils don't expect to work for their qualifications.
On top of all that, discipline has gone to hell: by the time I retired, my school no longer allowed staff to issue punishment exercises and the LA would only allow short-term exclusions for the most heinous offences.
I'll not reiterate my personal tale of woe here, but teaching staff and pupils are often facing horrendous behaviour these days.
We had one pupil who turned up for a prelim clearly under the influence of something - vodka, according to the other kids. The parent threatened to sue the school for suggesting that their little darling's behaviour was unacceptable. In the end, we provided separate accommodation for the actual SQA exam.
Shame for the kids whose prelim grades were affected by the drunken kid who yelled and clattered in the exam hall. I wish to God that the other parents had sued.