Are you ignoring the second part of the quote regarding Software sales being higher than 3DS, despite you saying decline, on purpose because it doesn't fit your argument?
Software sales are stronger than 3DS. No decline from 3DS to Switch in Japan in that regard. Only hardware is declining. The reasons are known.
I never spoke about a supposed software decline, that's why I'm ignoring it. It's not relevant to the hardware part of the decline, which was the main point of the discussion until then. I was only speaking about the hardware part of the market and software still going strong doesn't change the fact that handhelds are selling less and less with each new generation in Japan since the NDS.
So far, it was about handheld hardware. If you want to spread the argument across the whole market, be my guest. Just don't expect me to draw the correlation for you or follow through your weird attempt of moving the goalpost of the discussion.
I said consoles. Not the PS brand specifically because the principle is the exact same. You dont use the heighest point of sales and say something is in decline. No system will ever reach the PS2 but gen 7 sold way more hardware than gen 6 and gen 8 will be up over gen 6 as well. The Xbox brand only has 3 data points. How can you say its in decline?
There is way more to it than that. 3DS is the 2nd best selling system in Japan. DS is first. DS is literally untouchable. The Switch is trending behind the 3DS because the 3DS had an absolute price cratering because it was a shit product at its base price. The Switch has sold well at almost double the 3DS price.
You cant ignore the reasons.
I won't speak further about the Xbox brand, the console overall market or the worldwide gaming market, I prefer to say on the topic at hand, it makes the discussion less confusing. You were the one bringing it up, not me.
You dont use the heighest point of sales and say something is in decline.
The Japan handheld market is in a constant decline for at least 6 years, over 3 models and I'm not even including the PSP to Vita. Of course I can speak about a decline, because that's what it is, objectively, regardless of the reasons.
I'm not ignoring the reasons you or other brought up, I just disagree with those reasons being the explanations behind the objective decline. Some think the decline could have been prevented by X and Y, I think it would have happened regardless. Despite all the "Sony mismanaged the Vita" arguments, I still think the Vita wouldn't have reach the height of the PSP for example. I also think the Nintendo 3DS would never have sold as much as the NDS (you admit it yourself), regardless of its initial price-point.