The most popular genres amongst gamers (first-person, open-world, role-playing etc.) are generally the kinds of games that Japanese developers don't make because they lack the talent or ambition to do so. Western developers therefore reap the benefits of making games that most gamers want to play as well as making the games on the right of the graph (first-person 4X, turn-based strategy etc.) that the Japanese barely make at all so fewer and fewer gamers are into modern Japanese games. Japanese gamers are even apparently getting more and more into Western games:
Western Games Are Becoming More Popular in Japan
https://medium.com/skeptikai/western-ga ... 649fd13b12So Japanese developers will see their sales decrease as they mostly won't be able to keep up with Western developers.