Liefeld parted company with the publisher last month under controversial circumstances, later citing difficulties working with Smith among the contributory factors behind the move.
Smith recently announced his departure from DC, insisting it was under amicable circumstances, but Liefeld took to Twitter to offer his reaction regardless.
"So I walked out of DC due to my editor's incompetence. Now he's gone. Funny," the former Deathstroke artist wrote.
Liefeld also cited constant "editorial battles" and colleagues' frequent failure to meet deadlines as other reasons for his DC exit.
The illustrator has clashed with several of his former colleagues since leaving DC, including a bitter war of words with Batman writer Scott Snyder over Twitter.