For a historical understanding of where a lot of the mystery genre was in the first years of the 20th century, Sexton Blake is a key figure, but once you read a few of these you see why the genre really struggled to stand on its own two feet. Blake, a smug know-it-all, goes from puzzle to puzzle solving them with trivia-book level knowledge of science and deduction, without the emotional depth or even a charming central character. When people are annoyed by the mystery genre it's probably something like Sexton Blake that they're thinking about.