I agree with Miyazaki for the most part, and this is coming from someone who tends to enjoy at least one or two anime each season even in the current "recycled garbage age". While I don't think that anime should be solely comprised of "real/believable" characters, as I quite enjoy some of the more unrealistic portrayals of characters to an extent depending on the setting/genre, I do think that a major problem with current anime, if not the greatest problem with it, is that people don't see it as a medium, and in a practical sense, it really isn't, and can be likened more closely to a genre than a medium.
Ideally, it would be in the same category as TV shows, where being a TV show gives no indication of what it entails, and blanket stating that you don't like TV would likely garner some strange looks. Anime fails in this regard as you can ascertain a general idea of what someone's interests might be just by knowing that they like anime. It's rather unfortunate, but most people looking to tell a realistic story with human characters probably wouldn't even glance at using anime to convey their story unless the story was being told from the perspective of an otaku/nerd or someone who otherwise appreciates/relates to anime's currently most prevalent tropes and morality, because they wouldn't look at it as a medium, they would look at it as a thing for kids or nerds, and with the way that anime currently is, this is a rather justified way of viewing it, and I unfortunately don't see this changing any time soon, as it is likely easier to keep working on entertaining the current fans than trying to diversify and catch the attention of people who likely already have a fairly strong negative opinion of anime already deeply ingrained within them.
tldr; Anime practically isn't even a medium in the practical sense, and is more like a genre, and people's views of anime as a thing for kids/nerds and the functionality of the current systems will likely keep anime from diversifying beyond the otaku perspective for as long as people view anime in the way they do.