On (a), depends on whether you subscribe to the view the Modern Monetary Theory(MMT) is sustainable or a dangerous experiment that has unknowable consequences.
(b) Japan lacks natural resources (mineral, oil/gas etc.) and is hugely reliant on exports to keep the domestic economy running.
(c) There's a lot of cool stuff at a cultural level if you're a geek. Geeks are alas a small percentage of the population and that cool stuff is often kind of cool because it is a snapshot of the past. Not sure the curiosities are enough to keep the show on the rails.
(d) This one amused me. I recall IBMers talking about how IBM was one of the top companies by revenue right before it entered free fall and gave the tech industry to the modern tech giants. Kanban, Just-in-time manufacturing etc. were interesting and have their place. But something's gone wrong with the Japanese mindset. The thinking that produced interesting innovation back in the 70s, 80s and maybe even early 90s seems to have given way to a stagnant way of thinking that's evident everywhere you look. There's niches of creativity in things like anime but the innovation in technology and in process improvement that once enabled the amazing growth that Japan saw seems to have given way to a rigid way of thinking and a culture of just following the once innovative processes instead of continually improving them.
As for the voice controlled touch panel, probably not - but could the functions be simplified to less buttons and a more intuitive UI, for sure... unless you've embraced or complacently fallen into a culture of stagnation.
On your points re: China, they're innovating in ways Japan can only dream of without the fanfare or buzzwords. It's why most of the products we buy come out of Chongqing or Shenzhen. There's stuff wrong with China for sure but they're knocking it out of the park economically compared to Japan that's kind of riding the train over the cliff.
Re: The US etc., everywhere has issues but Europe/The US does not have the observable stagnation that can be witnessed in Japan. That's not about condescension but about looking at what I see with an open mind and not being afraid to make critical observations based on what I see before me.
I'd suggest Japan might be something of a warning for us in the West - if we stay complacent, keep worrying about superficial stuff that doesn't matter and let the core economic/innovating metrics trend in the wrong direction for too long we risk getting into a similar muddle.