Yaiba is a completely different game to begin with. They've said it from the beginning and yet people still don't listen. Apples to oranges and all that.
Imagine you have a bunch of people who like motorcycles. You start Motorcycle Gaiden, and the motorcycle folks love your product. Then, you made your third motorcycle model and it's not so good. People/Motorcycle Gaiden fans don't really like the new Motorcycle 3. So then you decide to add some spark to your brand name by making a semi-truck, outsourced, built and manufactured by another company, Truck Z. The motorcycle fans don't dig it. In fact, people who normally like semi-trucks don't really seem crazy about it either. At this point, the "it's supposed to be completely different from Motorcycle Gaiden" point just seems moot.
I understand you're good friends with some individuals in TN so you want to give them the benefit of the doubt, and that's great. But for most of us, $60 is a lot of money to spend. And look at it from my view after having watched almost the whole game on Youtube:
1) I don't like the artstyle
2) I don't like the writing/humor
3) I don't like how they handled one of my favorite game characters of all time
4) Critics (for what it's worth) don't seem to like it
5) Gamers who like the things I normally like (ie: previous Ninja Gaidens) mostly don't seem to like it
6) I don't think it looks like it would play well from what I've seen
7) It's really short
So, to say it's something separate from Ninja Gaiden is fine, but I also feel like it's fair for me to tell TN this isn't the kind of game I am interested in, whether it have the "Ninja Gaiden" brand title slapped on it or not. Without playing the game, I already know a lot I do not like, and nothing I do like (save one epic Izuna drop). Am I really expected to pay $60 just to be able to say that I don't like it with 100% certainty instead of the 90% certainty that I have now? Ninja Gaiden or no, the game seems to have little appeal to TN/NG's fans, such as myself.