Capone was dissed for two main reasons. First, he could not keep order in his empire. His outfit, although the biggest by far, was never able to stamp out the competition or even conclude a peace treaty that lasted. Chicago became the most violent city in the US for Prohibition-related crimes.
Second, Capone was a publicity hound whose antics aroused resentment among law enforcement and called attention to the fact that bootleggers and rum-runners (who were otherwise tolerated by the public because they supplied the public with booze) were really criminals after all. The famous 1929 gangster convention in Atlantic City was called by Longie Zwillman, Meyer Lansky and Charlie Luciano in part to push Capone out of the spotlight. Following the meeting, Capone arranged to be arrested in Philadelphia on a gun charge. He was given a one-year sentence in a PA prison, the better to let things cool off in Chicago and elsewhere.