I have been quite a fan of Bujinkan Ninjutsu for a while now and in fact, been researching quite a lot about Ninjutsu and its history. Unfortunately, as I started researching more into Ninjutsu, I discovered some interesting views from people regarding Bujinkan and to my surprise most of them were negative, calling Bujinkan Ninjutsu fake and ineffective. To some extent, I do believe that Bujinkan Ninjutsu as a whole, completely and absolutely, can't be a guaranteed form of self-defence, especially due to their lack of pressure testing. However, there are certain gems in this art form that I believe can be used practically and on a resisting opponent.
From my research of what the critic says about Bujinkan, I have understood this:
Ninjutsu itself is not a martial art but rather an art of espionage, spying, stealth and all things unconventional in warfare. But they did have to go through some martial arts training, as plan B to say protect themselves if they were caught from their covert operations. Given there wasn't any record of any special martial arts attributed to ninjas or that they focused more on the stealth and the espionage, they really didn't care to make their own form of martial arts but instead, dealt with the martial arts everyone was dealing with at the time. Which includes classical jiujitsu, swordsmanship, etc etc. While Bujinkan claims their form of martial arts was undergone by the ninjas of feudal Japan and that it is a special form devised by the ninjas.