I can give you specifics or I can generalize. Specifically there are thousands if examples of intelligence failures in Vietnam in my own experience and they add up to a failed war effort in general. In my experience Korean intelligence was better and British intelligence in Malayan emergency not as good. I doubt if you have ever been involved in a war but some of us were in a position to evaluate the intelligence operations of our wartime governments.
Looking at the WMD fiasco or the Comey thing I believe we can draw the conclusion that at least the present day intelligence services have become politicized. Intelligence officers regularly make the rounds of CNN and the left wing TV shows and bash the commander and chief. Does this go on in MI5 or the Mossad?