Bukowski had the nickname 'Buke the Puke' bestowed upon him by one literary critic and it stuck. It sums up one of the major criticisms of his work, namely that his subject matter is sordid. His stories are populated by alcoholics and prostitutes;some of his poems are concerned with base bodily functions such as 'Men's Crapper'. There is nothing uplifting about his work.
Secondly a fundamental criticism of his poetry is that it doesn't sound in the least poetic. He doesn't use rhyme, alliteration or any of the other familiar sound techniques. The opening lines of 'The Catch' are everyday speech (without much punctuation), including unpoetic profanity, divided up ino the poem's lines:
'crud, he said..
what is it?'
A final criticism is that Bukowski's outlook is immature. Consider the following lines from 'splashing':
some people are so dumb
you can hear them
in their dumbness. . . .
I want to
run and hide
To some this seems like an adolescent naively convinced of their own superiority.
On the other hand, Bukowski's work is very popular and he has been the subject of two Hollywood films!