The first hour you will be thinking, "WTF am I watching?" Be ready. It's more surreal than usual for Ghibli. It's like Carl Jung's "Red Book" or Nietzsche's "Thus Spoke Zarathustra." An old man nearing the end of his life, experimenting and pontificating outside his abilities to see what will happen.
The ending surely represents Miyazaki's relationship with his own son and the society he's leaving behind to him. ( I think. ) Miyazaki is infamously a tree hugging hippie and the talk of Japan repealing Article 9 of their constitution must have him rattled. And
Idk, 80% was just weird for the sake of weird and I may be reading too much into what little substance there was. It's really out there. Like Bowie's "Labyrinth" but more psychedelic. So, if you're into artsy and abstract stuff that explores the subconscious with no intended meaning like David Lynch's work or "Chungking Express" then check it out. Either way, gorgeous animation as always so you won't regret the time spent even if you're not super satisfied.