zlacker

It obviously has a shared history with the Spanish word (comes from Latin. The negative connotation in the phrase "facile piece of writing" would be "over-easy", as in: "over-simplified". ("Too easy" doesn't quite have the right connotation.)

When used derogatorily it also carries an implication that something is 'pretending to be easy' while not actually being so. It might also tie in with Facsimile, but that might be a false etymology on my part. Which I guess ties this back to pretentiousness, but not quite in the way you meant to :).