The one thing I really, really missed in Shenmue 3 was all the optional, missable scenes and sidequests that really added depth to the characters in the first two games. The conversations with Shenhua at night were very nice, but I'm thinking about all those little scenes in the first game, particularly with Nozomi, the cat and other characters that often resulted in cutscenes that add character development, but also the ones where you would engage in combat (or QTEs) or even learn new moves. And then there's Fangmei's Birthday, the duck races and the scenes involving Izumi and Eileen and the optional extra scenes you can see if you do the chawan signs at the 'wrong' cafes and restaurants. It really made your playthrough feel unique to you, but also added replay value. Or another example is how you can beat Chai in the arcade, but if you lose, the story progresses in a slightly different way.
Shenmue 3 in comparison felt a little 'a to b', linear and lifeless. I know it obviously had budget restrictions and they did the best they could, but it's something I hope they can explore a little more in Shenmue 4. I know there were side quests in Shenmue 3, but I don't feel they felt as organic, natural and as well integrated as they were in Shenmue 1 and 2.