An article (from OP's website) titled 'Poor kids need summer jobs, Rich kids get them' is interesting for a moment to the majority of readers and few readers who have kids looking for summer jobs will find relevant information in the article. The article mentions Brexit and UBI which are inevitably going to age. A month or years after release I would find better information in books on the topic or ongoing conversations with people following the topic.
Hindsight is easier on a target that stands still and less interesting too. We can unveil the significance of long running stories in the stream of consciousness format on HN or Reddit by revisiting stories that are repeatedly relevant.
When I want information that transcends time I go to philosophers, intellectuals, scientists, professionals in the field that have written years of accumulated knowledge into a book. I don't see what a news article seeks to provide that will age well. It's not aiming at creating information that ages well.
1. Given time to read and write proper investigative journalism, one doesn't have to resort to copy-pasting descriptive "news" from wire organisations.
2. With hindsight, it is easier to pick out which stories turned out to be significant, and which did not.
3. By revisiting past events, one can begin to unwind what greater consequences they had.
Essentially, slow news is a way to better understand what matters in the world. It won't let you talk about the latest soap opera star in the breakroom, but that's not news anyway, in my opinion.
I'm not sure the author agrees with this, but it's an attempt at answering your question about the value of slower news.