*Slightly edited because I misread a bit of what you said, but leaving most of my reply below intact.
I agree. The knowledge for ninjutsu is still preserved and passed on, but just be wary of people who are serious when they refer to themselves as "ninja" or "shinobi no mono" in today's world. Anyone still studying Ninpo today is a "Ninpo-ka", a student of Ninpo. But a lot of the knowledge can still be utilized in the modern day as Ninjutsu was primarily a set of strategies, not so much their own physical techniques as many people incorrectly believe. Ninja were Samurai, but not all Samurai were Ninja. From a modern sense though, in comparing Sumo, as it wasn't a battlefield art, it's still definitely closer to the real thing than any other Japanese martial art today.