...although these two movies aren't similar genre-wise , but taking a look at the two protagonists and their life, the similarities become more evident. In this movie the outcast can get a grip of himself through the help of whatever you call it: his imaginary mentors, his source of inspiration or just his own will to do something brave, but as a result he becomes arrogant and narcissistic... like Arthur in 'Joker'. But the sole difference between the two being that 'Ryoichi' (this movie's protagonist) doesn't become violent.
And I also want to point out that Sono's movies tend to be shot with much less care for detail and and are more rushed (partly caused by the small budget of his films) than high budget hollywood movies, that's why people might see that quality-wise this movie isn't on par with 'Joker', which I get, but still the message of both movies are very alike, which is what Sono seems to focus on it seems.
And I also want to point out that Sono's movies tend to be shot with much less care for detail and and are more rushed (partly caused by the small budget of his films) than high budget hollywood movies, that's why people might see that quality-wise this movie isn't on par with 'Joker', which I get, but still the message of both movies are very alike, which is what Sono seems to focus on it seems.