Interesting, I thought the exact same thing when I was playing KI:U - that this is the spiritual sequel to Star Fox 64 that I've always wanted. KI:U is like Star Fox Assault but actually good. SFA was dumb. KI:U is a masterpiece. The rail shooter segments are great, the land combat is great, the characters, the world, the monster designs are all inspired, and the script is surprisingly laugh-out-loud funny and oozing with charm.
The only problems are that the controls are a little hand-cramping and some of the platforming segments are really fiddly (Pit dashes way too quickly and winds up falling off stuff way too often as a result). Otherwise it's pretty much perfect. I didn't have that much of a problem with the controls actually, I don't find them hard to use, I just don't want to play the game for more than a couple hours at a time.