They go all Trot, and declare that the project was somehow not "bottom-up" enough, that it wasn't enough of a "grassroots democracy", that it lacked "genuine mass participation", etc.
These are all just worthless soundbites.
Obviously, an organisation with half a million members needs some degree of professionalisation, and, yes, that also means that there will be an internal bureaucracy, and not everyone will be directly involved in everything all the time.
But in this case, it worse. Because it's not even true on its own terms.
There WAS a Corbynite mass movement. And there still is. Twitter is little else but the digital church of St Jeremy. There's the Canary, Skwawkbox, Evolve Politics, Norovirus...
No. They did not. But what have been different if they had? Where did they ever disagree with him? They loved everything he said.