More science authors should read writing advice like this.
Older papers that are considered notable today would probably be well-written compared to a random paper published last year, even if there weren't any group-level differences.
To be fair, given that the papers-published-per-scientist-per-year metric has been increasing (somewhat unhealthily, so it seems), I wouldn't be surprised if there has been at least some decrease in writing quality, simply to due to less time spent editing and polishing.
It’s also interesting how formats have evolved. Older journals like Nature and Science used to have a “letters” section--essentially letters to the editor. They were brief (200-300 words) and started with “Dear sirs”, like an actual letter. Today, a “letter” in the same journals is essentially a whole (short, 2-3 page) paper, like this one: https://www.nature.com/articles/s41586-019-1578-4
Godel Escher Bach is a book that was enthusiastically written with a word processor. And that explains a lot about it.