This is a terminology issue. It's true that NPR isn't "leftist" in the eyes of many people on the left who endorse socialism. However, NPR is definitely liberal, which leans left on cultural issues, and often centrist or slightly to the right on economic issues. The sterotypical upper-middle class, urban, liberal professional is always an NPR listener.

So I understand your disagreement: NPR is not generally going to criticize our system of capitalism. After all, many liberals - particularly the opinion-making elite - are thriving in this system.

But they will always approach cultural issues from the left liberal point-of-view. Recently, NPR Opinion has swung even more to the left: just listen to their afternoon talk shows. All Things Considered and Morning Edition have not gone as far, and are more center or center-left. Allsides, the media bias organization, agrees and rates NPR opinion as "Left" and NPR News as "Centrist":

https://www.adfontesmedia.com/

I think leftists replaced actual arguments with sarcasm sometime around 2010.