Because it is meandering, lacks a clear focus and organization, falls down tangents, etc.
People who are excellent writers within a professional system where (1) they aren't writing about themselves, and (2) have the support of professional editors, etc., before the public sees the work, often have much lower quality without #2 or when the context is far from #1, such as writing about personal incidents that are highly charged. And most especially when both of those occur at the same time.
And I don't claim his writing in the general sense is poor quality, I say that the four-part epic on this incident is poorly written.
Or maybe it intends more to graphically convey the flow of consciousness that results from extreme indignation more than to inform effectively about the author's side of events, in which case it's a masterpiece of written art. “Poorly written” definitely makes an assumption of purpose that may not be warranted: as a show-not-tell feelings piece it is tremendously effective.
I thought it was a well-written account of his experience.
But for media insiders, they know who these people are and find the additional detail useful/entertaining. I am in the former camp and wish there had been a timeline or TLDR.
And the intended audience is clearly people who care quite a lot about the "inside baseball" of NYT/Journalism and the media more broadly.
So how the general reader perceives this is irrelevant. It wasn't written for the general reader!
I don't read articles in the New England Journal of Medicine and claim the writing is poor because...it's not written for me and I wouldn't even know where to start in critiquing it.