I haven't read the article, just the snippets in the original post. But I'm guessing there's no study to accompany this, where they show a bunch of statistically significant samples of rookie performance in their first X games in, say, the 1970s, 80s, 90s, 2000s, and then compare the data to the 2020s with a clear trend line that it really is more difficult to break in today?
Because without that, this is more-or-less a fluff piece speculating on the causes of an effect that nobody has shown to actually be true.