On the one hand there is some lovely, fetching detail in the visuals, definitely including backgrounds and settings of all varieties, and also secondary or tertiary active elements, like a passing dragonfly, a toy gliding through the air, or a subtle cue in the last moments. On the other hand, even allowing for different cultural sensibilities about how animals might be anthropomorphized, there is a curious lack of detail and texture in the appearance of most any character. Just as much to the point, even allowing for different notions of how This Or That might be animated, some minutiae like characters' mouths can only be described as "ghastly." In fairness, that's true of any mouth, even in real life; the next time you're talking to someone, keep your eyes on their mouth and see what I mean. And I can't judge any facet of the animation too harshly; more than not it's just fine, some character designs are better than others, and anyway, the art form was still developing in fits and starts.
It's not so easy to be so generous about other aspects of 'Momotaro's divine sea warriors.' There are troubles in the visuals and especially the audio beyond the graininess and lack of total clarity that comes with contemporary technology and the ravages of time. There are small shots and scene of frivolous nothing that serve no apparent purpose but to pad out the length, and these also tend to look worse than the material that is plainly more purposeful. Sometimes the manner in which the camera pans across a scene is weirdly unnatural and off-putting. Elsewhere we'll have long, awkward pauses in which the meaningful audio drops out save for some ambient noise, and it quite pointedly feels like Nothing where there should be Something. This feature isn't the only instance I've ever seen of such matters, but the one other that specifically comes to mind is not a favorable comparison; one way or another, that decided lack of polish just comes across as incomplete, or crude.
Another issue dragging down the film is the notable variability of what it is presenting to us. There is a wild mix throughout these seventy-four minutes, sometimes juxtaposed and sometimes smashed together, of lighthearted silliness befitting any given cartoon that's built for children's entertainment, and the slightly more serious cartoon note of "uh oh, our friend's in trouble, we better help them." There is glorification of Japan, and accentuation of united purpose for a greater cause; performance of wartime duties, maintenance of wartime camps and equipment, and ultimately the commencement of an operation. There is also a history lesson that's narrated over its own distinct art style; an educational segment that would fit right in with any given episode of 'Sesame Street'; and musical sequences. Most of these bits and bobs are fairly well written and animated in and of themselves, and some underlying themes and bigger ideas are genuinely admirable. By putting them all together into a single movie, however, 'Momotaro' sacrifices some sense of cohesiveness.
Granted, despite the mix and match of the writing, it's not possible to mistake 'Momotaro's divine sea warriors' as anything other than the propaganda piece that it was for Imperial Japan during World War II. This core gets peculiarly waylaid every now and again, but it's the primary thrust of the title and heavily, increasingly dominates the latter half. Still, I have to wonder just how effective it could have possibly been in its purpose considering how we swing from "tee hee, chasing a hat that's caught on the wind!" to "no, for real, this is war, and here is a battle with explosions and gunfire." I know the average short from 'Looney Tunes' or 'Merrie Melodies' was also sometimes disproportionately violent, but this exists on a level all its own. Regardless, the messaging is right there for the taking - and in light of the course of history, the picture now exists as a novelty, and a vestige of another time. We can in turn appreciate and criticize the animation and writing in and of themselves, but at the end of the day, it's only the avid cinephile or a history buff who will have any reason to revisit this. Despite its nature, I don't think it's so simple as saying "'Momotaro's divine sea warriors' is bad." I think it's a film at odds with itself. If your curiosity is piqued, as mine was, then by all means check it out, but otherwise you can just not bother and get on with your day.