This is true, although there are some slight indicators we can look at.That's not particularly true...Shenmue I sold around 400k each between Japan, North America, and Europe. From then on, the only real data we have to compare is Kickstarter backers for Shenmue III, and breadcrumbs of hard numbers, such as that one Spanish chart and that one Japanese chart for III. Anecdotally, Shenmue is more popular in the west nowadays than in Japan, but we don't really have any factual data to back that up.
When it comes to Kickstarter backers for Shenmue 3, only around 3% of all total backers where based in Tokyo. Granted, this may have been skewed a little by Kickstarter being a Western site, but it was still heavily publicized over here when it was first announced and so most Japanese Shenmue fans were likely aware of it.
Likewise, the sales figure, although incomplete globally, clearly show a huge drop off in the number of Japanese people purchasing the game when compared to Shenmue 1 and 2. We can’t say how this compares to the rest of the world, but when establishing the series’ current popularity in the East, I think it shows an obvious trend.
To be honest, I’m not quite sure when/where @Tsukuyomimagi99 is quoting me from in his post, but I definitely agree with what he is saying. My previous job brought me into contact with a lot of Japanese people and I would regularly talk to them about video games. Pretty much all of them had heard of the Yakuza series, but very few knew of Shenmue; let alone liked it.
That said, I do disagree with some of the posts I’ve seen about the marketing of both Shenmue 3 and the Shenmue 1 and 2 remasters over here. A few people have said that there was very little promotion for them, but I saw a decent amount for both releases in a number of districts across Tokyo. Granted, there was nowhere near as much as there is for “big” releases like Smash, Monster Hunter and Animal Crossing, but for a remaster of two twenty year old games and a glorified indie game, I think they each got a very fair showing.