I suspect that the market and capitalism has had a hand. In my youth, I remember opinion pieces being marked quite clearly in newspapers, and in general it seemed like there was a sort of a popular, chatty, slightly-pompous style they were usually written in. I.e., it was pretty clear what exactly they were, and by that very nature, it allowed the writer to have some real fun with the premise.

Over time, my guess is that the faster nature of modern civ / society combined with capitalism skewed things towards dropping much of the former signal language, and treating news as more of a pure product, with a certain deception and advertising built-in to drive engagement and revenue.

On a side note, my take on scientific papers is that they're generally very difficult for laypeople to understand (hand raised here), and need a certain trained class of news-people to represent them accurately, simply in terms of what the paper is about. But more than that, even more specialised people are needed to put the paper in to full context, considering the publication, peer-review level, and junk science possibility. Unfortunately for the public, I'm not sure those people exist in any significant quantity.