Primarily doesn't mean exclusively in my book
No I don't agree, and think he's strawmanning quite a bit (though that happens of course with a lot of criticism of the political opposite, from every side). I don't know any leftists (got a problem with the term liberal, too confusing depending on in which context it's used), or any person in general that believes that any perfect world would be possible, perfect institutions or not.
And both groups deal in tradeoffs, what differs sometimes completely is the way different tradeoffs are regarded in terms of their effectivity in improving human welfare overall. It's a very popular strawman argument that the left believes in perfect solutions, no one to my knowledge does. They just believe in improvements, as does the other side, the difference lies primarily in how to achieve those improvements.
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It's impressive how much ground he gained the past few weeks there though.
Still think that he's only got very slim to make the nomination sadly, but his campaign is still an important and powerful message if nothing more.