"consumerist capitalism is an environmental disaster" isn't a hard argument to make and people eventually realize most environmentalism is just stacking the deck chairs on the titanic.
Sanders wasn't getting on the stage demanding we nationalize all our businesses. I never heard him mention a 'vanguard party'. I don't think I heard him say, "Businesses need to be run by worker councils, exclusively".
It's one thing to say, "I don't like the idea of democratic socialism/social democracies", but those ideas are hardly 'radical socialism' or 'full socialism'.