Okay, and those first two years were six years ago. That's the point I'm illustrating here; you're saying the sales this year are a "concern" because they are lower than the first two years of its lifecycle, when the system is now in its eighth year of availability in Japan.
Switch already had its sales surge years ago, different times and periods in different markets. You are acting like the sales rate in this 8th year is somehow an indicator of platform collapse, when it is still regularly outselling the PS5 2:1 if not more in the region on a weekly basis, so what does that say about PS5? And yes I include PS5 here (and Xbox, for that matter, but they're a non-entity in Japan) because in these sales discussions there's usually a point of comparison to measure against. PS5 is the only other traditional gaming device being actively sold in Japan, so that's the comparison.
I think you & OP are greatly exaggerating how "bad" the sales slowdown actually is, and it's goofy to try pinning any of it as indication for a lukewarm Switch 2 performance in the market or globally.