Okay...and you are presumably aware that every government since the 60s has tried to reform the Civil Service? And how has that gone?
Parliament is not sovereign because this is an administrative issue. As I explained, elected officials have limited direct control over ministries. And an even bigger issue is that the Civil Service is unionized, so if you were actually looking to reform it wholesale then you would have to shut down government for months with irreparable damage done in the media by civil servants briefing daily against you...so I am not aware of a way to do this. You can't reform ministries, you can't reform the whole thing...so what is the solution?
The reason why politicians blame the civil servants is because they are bad. No-one thinks otherwise. The past three heads of the civil service have acknowledged there are massive issues with competence at every level, this is not new. But it isn't possible to reform.
I am not sure how anyone can think Parliament is sovereign in this matter either. It makes no sense based on the evidence of repeated issues with competence and multiple governments being unable to fix that.