Not every criticism of capitalism is communism.
But also, is it any wonder that a platform built without a profit incentive and centred around the concepts of mutual voluntary interaction rather than hierarchical control would attract a more anti-capitalist userbase?
There are many ways that societies can work. Criticising the way society currently works is not criticising all possible societies. The options are not "accept things the way they are" and "bugger off into the wilderness".