It is kind of sad that the "longform content" that you mention as the new thriving alternative to traditional media, is rather time-infefficient audio and video. I regret the dearth of longform reliable text.
it's not that hard to summarize: a rendering engine transforms html into pixels on the screen. most people will have at least a vague idea of what html and pixels are. there's no further need to dive into the details where that description is less than 100% accurate (e.g., sreen readers).
that's to say, the reporting is just lazy and uninformed. no need to bail them out with a technical excuse.
I doubt very much the average person on the street has a clear idea what a pixel is, let alone what HTML is. And even your description is so incomplete it's wrong since the safari engine also includes JavaScript execution, media rendering etc. on safari, proving my point: if you try to simplify it for the average reader, your description ends up wrong
Screen readers are a distraction. Even completely blind readers would have a concept of what is displayed on a computer monitor even if they've never seen it.
but none of that stuff matters for reaching a reasonable conclusion. we don't need to know how a transmission works to reason about speed and acceleration, only that it converts power from the engine into velocity somehow. the whole purpose of abstraction is to take advantage of such decouplings within a brain limited in how much information it can hold in working memory in any one instant.
The amount of text necessary to explain to the average NYT reader what a rendering engine is probably more then the allotted text size for this piece of pseudo-intellectual garbage. Should make you worry about everything else journalists write with the same lack of care and understanding of details.
This is why podcasts and longform youtube content form actual experts is thriving while traditional media is dying. They have optimized so much for short attention span, clickbaity and inflammatory content that they have lost all resemblance of quality and expertise. In short, for any given topic, if the explanation is less than an hour long discussion piece, it's almost guaranteed to be simplified to the point of being wrong and useless.