I never fully understood [the label of 'escapist'] till my friend Professor Tolkien asked me the very simple question, 'What class of men would you expect to be most preoccupied with, and most hostile to, the idea of escape?' and gave the obvious answer: jailers. — C. S. Lewis
Escapism gets a bad rap when talking about fiction. Thin, fluffy, etc. The famous quotes by Tolkien and Lewis underscore the problem.
Then, I was pondering the matter one day -- bad habit there, hard to break -- and considered what you would put in instead of escapism. The complaint is often made that it does not go into Relevant Issues, or other Deep and Meaty Matters.
That means, it doesn't contain enough of the author's thinking. This leads to the same problem as sagacity: it is a lot easier to create a diverting story than to create a profound one. To be sure, keeping it out of the lecture mode does mean that it's not infringing on the story structure as such -- if you manage to get profound without lectures. The problem is that it is very, very, very difficult to be profound. It is an easy oppurtunity to show off the depths of your shallowness, and do so by twisting the plot, flattening the characters, and draining interest from the setting to fit the theme.