Creator Backlash: Despite its popularity, Miyazaki doesn't have too many good things to say about this film. But that's pretty standard for Miyazaki – the guy is infamous for both his insane work ethic and his grumpiness; he doesn't have much good to say about any of his work.
Vindicated by History: Given Cagliostro's reputation as one of the best animated films ever made, one may find it hard to believe that it flopped during its initial release in Japan… but it did. Audiences were used to and expected the lecherous Villain Protagonist Lupin from the comics, "Green Jacket", and Mamo (which had done very well the previous year). But Miyazaki intentionally made Lupin a Lighter and Softer true "gentleman thief", irritating the preexisting fanbase. It was only years later that fans came to appreciate it on its own terms.