It’s hard to say until we get an in-depth retrospective of the games development but I theorize it had something to do with the way the game was initially funded and then how partners like Deep Silver and right at the end Epic came on board and provided additional funding.
It appears they took the delays and extra funds to flesh out and iterate both Bailu and Niaowu but ran out of time and potentially funds to create a truly fulfilling ending thus why the Fortified Castle felt unfinished and rather abrupt. I believe Cedric has confirmed that the ending wasn’t what was originally planned so clearly some serious cuts were made.
It’s something I think a lot of us have wondered out loud since the end of Shenmue 3. Now while Ryo’s ability as a martial artist has significantly improved he’s still clearly no match for Lan Di. For that I am thankful the game kept that consistent logic, however how does he ever hope of getting revenge and taking on the other members of the Chiyoumen and keep that journey somewhat plausible?
A Grandmaster somehow unlocking Ryo’s latent talent or ability? I was struck by line by Master Bei saying
martial arts can’t be learned overnight and the third game in particular goes to great length to demonstrate this, so this seems unlikely. Of course many of us have speculated Ryo won’t be able to beat Lan Di in a traditional way, so unless there’s a giant time skip (something the original GDC Shenmue talk dispels) it doesn’t leave Yu a lot of plausible options.