Why did many great poets in ancient times fail the imperial examination?

Great poets are very talented, but great poets may not be admitted. The imperial examination only tested a small number of poems, which had a lot to do with the examiner's hobbies at that time. Many great poets may write well, but if they are not to the examiner's taste, they will easily fall off the list. Moreover, the more talented a poet is, the more real he is, the less he pays attention to the content in his writing, and the more likely he is to commit taboos, so many great poets fail to pass the imperial examination.