As someone who was part of Cartoon Fantasy Organization back in the 80s, I agree. I mean, as far as plotting and characterization goes, a lot of the anime n the 80s was really shallow. I mean, and this pains me to say, if you look at say, Bubblegum Crisis or other classics, and the plot isn't all that. then again, plotting and deep characterization wasn't the point of those shows.
Right now, I think we're looking at major peaks and valleys- the best of the current crop, like Natsume Yuujinchou or In/Spectre are incredible well done, as good as anime ever has been. it's just there's a lot of anime in valleys, and those valleys are deep, and full of crap. As for the average, how can one even compare the averages? The most popular anime series is still Sazae San. So even if I basically agree with Miyazaki, I'm still sanguine, because I still think there's the potential for really incredible stuff to be made.