I vastly prefer Shenmue to Yakuza, but that doesn't mean I don't want to continue the Yakuza series. As OL said, I find Japanese gang politics to be really fascinating, and I never really gave it much thought until I played the Yakuza games. It's similar to how Shenmue piqued my interest in Chinese culture.
I think they're both great but they are also very different from one another and it doesn't have to be a "one or the other" type of thing. Of course, if you don't want to play them, that's fine. I just don't see why Shenmue coming back makes Yakuza pointless to play.