I think this is the third feature-length documentary I've seen set in Studio Ghibli, and I'm learning that the behind-the-scenes stories there are often just as interesting as the stories the studio tells in its films. That's doubly so for this documentary and The Boy and the Heron, which overwhelmed me when I first saw it. I remember reading about the film's autobiographical elements, and then it all clicked on a second watch. This documentary does indeed confirm much of the meaning behind The Boy and the Heron, but not without giving it all away. It's not a film about explaining everything, but you do get a good deal of context and insight anyway.
It also gave me added appreciation for how hands-on Miyazaki remains as a filmmaker. There are other directors making films in their 80s or older, but I doubt many of them still have the same kind of intense creative control they might've had back when they were younger... or they do, but they've lost it a bit skill-wise (sorry Coppola, Megalopolis was a blast at times, but also super sloppy). Miyazaki is still the author of the films he makes, and if his latest shows us anything, he really hasn't lost it creatively.
Also, this is probably Hayao Miyazaki at his most human. He's been a funny, kind of grumpy old man/genius in the past, but you really feel for him at parts throughout this documentary. It doesn't shy away from getting old, losing motivation, and facing the idea of friends passing away at a moment's notice. The editing really makes a good many emotional moments here hit harder. I come away from the whole thing even more thankful that Miyazaki got to finish The Boy and the Heron and that it came out so well; maybe even one of his very best.
Also, this documentary is probably a tad too long and sometimes repetitive, but much of it's engaging. Just saying that because I don't think it's perfect, but it was very good, and a must-watch for Studio Ghibli fans, or anyone who wants to fully appreciate an artist like Miyazaki.