The Devil's Dictionary paints the 'studious' as bearing an 'ignorance' that sets them apart from the common man.

If the word 'studious' refers to those who are 'schooled' (i.e. men of learning), then I take the sentence to be charmingly mocking of those who are 'experts' by qualification (rather than ability): credentialed ignorance.

Mark Twain has remarked on this before, in his own characteristic way, when he distinguished his learning from his formal studies:

I have never let my schooling interfere with my education.

The above statement made me double-back the first time I encountered it. It's an insightful distinction, and not one I would have made myself.

Later I discovered this gem from William Hazlitt:

Anyone who has passed through the regular gradations of a classical education, and is not made a fool by it, may consider himself as having had a very narrow escape.

I am inclined to agree with all three sources.

Those with education but lacking experience - i.e. the 'studious' - are often out of touch with reality. Over time, their intellectual rigidity becomes apparent; they tend to be opinionated bikeshedders, contributing to form in discussions, but not to their pith.

Dogmatic expertise may obscure truth.