If we say that Shenmue 3 sold around 300,000, I think it has the potential to reach at least 1 million. At least 1 million gamers like the slower stories where the player has to think and immerse himself in the game world. There are many similar Shenmue games that sell a million. For example, Life is strange True Colors is a game that takes place in a small town, all NPCs are unique, everyone talks... Locations and shops are full of details. Of course, Shenmue is a much more epic game, but I gave the example above with the idea that there is an audience that enjoys such games.
I think the audience that would love Shenmue either doesn't know about the game yet or is afraid to try it. :)