You know, if we extend this out, it actually puts out an interesting scenario.
Traditionally, the decline in the Japanese dedicated device market has been viewed from the perspective of lifestyle fit. Handhelds were seen as working better for Japanese lifestyles than consoles, and mobile devices were seen as working better for Japanese lifestyles than handhelds. As handheld games became sufficiently high enough quality across a wide range of genres around the DS/PSP era, Japanese gamers migrated to handheld devices, even if it meant trading some amount of perceived quality. The same happened with mobile devices usurping handheld devices 8-10 years later.
However, it's actually entirely possible that Japanese gamers just felt that handheld games on the DS/PSP were flat out better than the offerings on consoles during the late PS2 and full PS3 era. Similarly, they might view mobile games as being better designed and more fun than anything consoles or handhelds have to offer today.
Who is to say that Dragon Quest Monsters: Super Light simply isn't just the far superior game to Dragon Quest Monsters: Joker 3, causing the latter to decline? Maybe Brave EXVIUS is way more entertaining than FF15, helping to push FF15 notably down even in terms of sales versus install base. And maybe Dragon Quest of the Stars just turns out to be better and more fun than Dragon Quest XI, causing declines there
I don't think those would be popular opinions here, but we actually don't have much opinion data from people who have dumped consoles and handhelds in favor of mobile.
In an anecdotal perspective the general buzz surrounding Fate/Grand Order seems to be far livelier than any games released on dedicated device, except Pokemon. I feel people talking F/GO the same way they were talking about, say, Final Fantasy X years ago. F/GO and others like Granblue feels like a living community with new stuff to talk every month while the talk of console games died a few weeks after its release.