Is this because we're importing lighter content from Japan, or is it an engineered plan on their part to produce more marketable media?

Probably a bit of both but probably mostly the former. There is a lot of good anime based on Japanese history and traditional arts etc, and anime is well still primarily made for the domestic market, right?

Really, this is probably a decently-sized part of why I've tended to favor "going off the beaten path" when it comes to anime, because if I am going to be watching cartoons from a distant country, then I want to feel like I'm Not Supposed To Be Here (cue Half Life 2 airboat music) rather than feel like the cartoons have been curated for me to prop up the PR of the Fascist War Criminal Shrines Country.

...Well, I say this, but my first anime was literally funded by the Japanese government, and was on Netflix.