I only think fighting games are hard if you've never seriously understood one. But even that can be quite hard, since only a handful of fighters even come with in-depth tutorials. Even then it can be less fun if you don't have someone who is close to your skill level or is willing to accommodate. Its a good thing that KI has a good tutorial and I really hope more fighters do it too.
Also I imagine that going from DOA to KI is a pretty hard swing. I've only played a bit DOA5 but, the execution in that game seems way easier to learn to do easily than the 6 buttons and various fireball and shoryuken motions that most fighters require. I had a similar problem trying to teach my friends Skullgirls after them having only played Smash Bros and Soulcalibur. So I guess if you wanted a pick-up and play games with friends, KI doesn't really fit unless you all understand the basics and are on somewhat equal footing. All I can say is, try to get them your friends to learn it with you and see if you all like it.