Having worked in this area for 10 years.....
NHSD got pruned back in 2018 and is now boring but competent, more often than not their apparent deficiencies are as a result of being hamstrung by policy they did not create.
NHSX was created to be an internal consultancy, not bound to any other part of the organisation, but has turned out to be a cesspit of weapons-grade incompetence, staffed by ignorant strutting wastrels, many of whom were refugees from the original CfH train wreck. It makes the Covid PPE procurement look like a paragon of public-spirited transparency,
NHSE thinks it knows what it wants, but doesn't. There are a lot of people in charge who want shiny stuff to show ministers and don't care about whether it is actually true or not. So we have glossy Tableaus coming out of our ears, fed by random rancid data that is months old. And people are wondering why the whole thing has fallen over in a chaotic heap.
The root cause of this is that when the NHS created its payscale, IT folk were put on the administration/ clerical paypoints, rather than the professional / technical ones, and as a result anyone remotely competent has left for a proper salary, bar a few true believers.