From XR's own lips

 From Extinction Rebellion's Twitter

"Just to be clear we are not a socialist movement. We do not trust any single ideology, we trust the people, chosen by sortition (like jury service) to find the best future for us all through a #CitizensAssembly A banner saying ‘socialism or extinction’ does not represent us"

XR sees talk of ‘capitalism’ and ‘socialism’ as politics while they see themselves as ‘beyond politics’ urging all people to bring pressure on governments to do more to tackle climate change.

 This means that they are basically a pressure group employing direct action and civil disobedience tactics to get capitalist governments to adopt a particular policy.

Leaving the way out to citizens assemblies is a cop-out. For all the merits of such assemblies and their potential usefulness in decision-making in a socialist society, today, most citizens will have the same ideas as they express in elections, i.e that they see no alternative to capitalism and so would come up with proposals to be implemented under capitalism.