the shenmue engine dates back to 1998, thats 6 years ago! and even that was a modified version of the saturn engine that dates back to 1995! shenmue III is going to look very outdated compared to games that get released nearer the time to shenmue III. and they dont have enoughg money to make another engine for it
also sega don't have the budget for the same ammount of detail to be put into shenmue III as was put into I and II.
this is going to remove any newcomers to the game, becuase shenmue III is going to look so poor