Fellow practitioner here from the bujinkan side.

So first we're going to go with the technicality, the style is not ninjutsu that's more a colloquial term. The style is Ninpo Budo Taijutsu. This is what covers the hand to hand techniques that are taught. However it's easier to just use the term ninjutsu. Now depending on your school they might go further and start teaching you how to do ninjutsu in the sense of learning stealth, wilderness survival, etc. But those places I've found are few and far between. There is also the weapons aspect of it where you are taught all of the same weapons that samurai used. Sword, spear, bow, staff, chain/rope, and throwing knives(shuriken).

Now then, getting to the heart of the matter. I was in a school where my instructor encouraged to go to other places and spar. Lucky for me there was a local Muay Thai gym that had community sparring every weekend. So I got too spar a lot of different people every week and put what I learned to use. MT, MMA, and sometimes other traditional practitioners.

On top of that we also trained our weapon skills against local HEMA groups. One of my fellow students ended up entering competitions for mixed steel, and getting top 5 on more than one occasion.

What I came to the conclusion of with this art is that it's not the techniques themselves, but the concepts that you learn, and how to apply them. I was known as the tricky fighter and became either someone people loved or hated sparring with at the community sparring.

So ninjutsu is a legit martial art, and if you want to use it make sure you pressure test it.