Miyazaki was a communist until the fall of the USSR. And while he ditched ML like a lot of people unfortunately did in that post-soviet period, he's since said a handful of times that he still considers himself a socialist, generally.

So, looking at most of his movies, they're stuffed full of leftist themes.

Kiki's Delivery Service is very much about Alienation under Capitalism. Kiki's hard work ends up burning her out and straininh her relationships with others, because she's commodified a thing she loves: flying, in order to survive. And the movie contrasts that with the lesbian forest painter Lady who works hard on her art, on her own terms, unburdened by the whims of capital.

Spirited away has too many themes to count, but let's look at the design of the bath house. It's mostly a Meji-era architectural style, but when Chihiro goes up to ask for a job from the witch who owns it, the architecture is suddenly very European. So visually, we're being told that the west is literally lording over, and owns, Japan.

And a persistent theme is also the ways Japan is disconnected from its culture. Chihiro doesn't recognize the spirit shrines, unceremoniously dumped by the roadside at the beginning of the film. And characters say of the train that it "used to go both ways, but now only goes one way". The train is death. Spirits can only go further into the spirit realm, and never back to visit earth.

And put together, the film is pointing to Japan's disconnect from its own history and culture due to US imperialism.