1) Their left leaning narrative can't take facts at this point.
What facts can't they take? What's the narrative that NPR is trying to weave? As others have already mentioned, their coverage is often not favorable to the left. NPR syndicates content from hundreds of independent public radio stations, including other public and for-profit sources such as American Public Media, AP, Reuters, ITN, etc. Are they all conspirators in this narrative?
2) The sheer amount of lean really comes out of their choice of what to cover.
Is OP suggesting that NPR and the hundreds of other public radio stations suppress topics so as not to appear "left"? Also, see #1.
3) They know it's easy to just offload comments onto another service.
They are already offloading comments to Disqus. The problem is not technical but managing and moderating the vast deluge of spam, trolls and other bad actors.
4) Any news source w/o comments is basically propaganda at this point.
As others have already mentioned, their coverage is often not favorable to the left.
And often is, up to and including misleading and misrepresenting facts. I gave two examples earlier, and was unable to find a retraction of either.
Is OP suggesting that NPR and the hundreds of other public radio stations suppress topics so as not to appear "left"? Also, see #1.
Mass uncoordinated action does not imply conspiracy.
Are they all conspirators in this narrative?
As I just said, "conspiracy" is a fundamental misunderstanding. But now that it's on the table, for things that make you go "hmm", look who the major media (news) companies make their political donations to. You'll find an interesting pattern. NPR excluded for obvious financial reasons, but still, there's a pattern.
This is just hyperbole.
I am not so sure. Comment sections serve an important purpose of allowing bullshit in the article to be called out, "trolling" and "bad actors" be damned. I also find it interesting how often those labels are trotted out dismissively against people who disagree with the point trying to be made, and how this "civility" canard is held up as an excuse to silence all discussion.
Is the OP correct or are they not? If we want to have a discussion, let's start there.