This is from a while back, but the folks at The Spectator posted this excellent take-down of mediocre critics:
We therefore very often find, that Persons the most accomplished in Ridicule are those who are very shrewd at hitting a Blot, without exerting any thing masterly in themselves. As there are many eminent Criticks who never writ a good Line, there are many admirable Buffoons that animadvert upon every single Defect in another, without ever discovering the least Beauty of their own. By this Means, these unlucky little Wits often gain Reputation in the Esteem of Vulgar Minds, and raise themselves above Persons of much more laudable Characters.
If the Talent of Ridicule were employed to laugh Men out of Vice and Folly, it might be of some Use to the World; but instead of this, we find that it is generally made use of to laugh Men out of Virtue and good Sense, by attacking every thing that is Solemn and Serious, Decent and Praiseworthy in Human Life.