That's a spectacularly weak criticism. Look, if an election is called and Corbyn doesn't throw his weight behind a 2nd vote, I'll have to concede with a heavy heart that a potentially great PM has choked on the biggest issue and place my faith in someone else. But until then, with the Tories pausing their backstabbing only to block an election, there is nothing Corbyn can do, due to cold parliamentary arithmetic and May's stubborn refusal to seek cross-bench consensus.
Maybe a Corbynista would hate me for making him sound impotent here, but you can only criticise someone for what they can control. He can't fix this by himself.