Why slice of life matters
You wrote: ..."there is only so much supernatural content that you can consume before being worn out by their unrelateable issues." I couldn't agree more. One can only take so much Anime and cyberpunk before it begins to grow unconvincing.
Yes, I haven’t seen this one but it WAS shown as part of a Ghibli retrospective here in Vancouver. For the absolute Japanese master of the family dynamic and also possibly the greatest filmmaker of all time, watch Ozu films.
It may come to be that "MNtY" turns into one of their most-loved movies; if not by Ghibli aficionados, but the wider public. One thing I've noticed is that 'mundane' movies /TV shows are particularly cherished by people who have chaotic, stressful lives, who crave the representation of some form of 'normalcy' as a break from their struggles. The "excitement per minute" thing also resonates; so much modern culture/entertainment puts demands on your emotions in a spiraling arms-race that I believe people are profoundly... tired of it. There's only room for so many "Final Battles Of Good VS. Evil" in most people's souls, before overload sets in; + we may be past that point (at least in America; Japan is of course different, but seems to move faster and be more excessive in terms of 'top-down' culture). One thing is unclear here, however; is "MNtY" a new film, or an older one? If it's new, that may explain its absence from the museum.
Classic Japanese cinema includes some of the most incredible slices of life put on film: Ozu, Naruse. Twenty-Four Eyes, The Naked Island.