I think it makes sense in their head that there exists a dichotomy between left and right (restricted to liberal/conservative in a very US-centric way) and that they are on the left of that spectrum. Then, being "as left as can be" is a matter of being more what they consider left, which, indeed, they are.
God, I forgot how annoying I find this phrasing they adopt, especially when you know they haven't done the least bit of reading to inform their opinions.
Something you said that really resonated with me is, besides the experience with psychedelics, the way that people will treat you as a conspiracy theorist for deviating from the "correct" frame. I think this is a major barrier for escaping the neoliberal narrative, as it is very natural for us to try to fit in, to not be weird, to be accepted. Nobody wants, at face value, to be the loony commie and ostracised.