They normally do so because of the countless number of sights that are being registered on a daily basis. If you were in their shoes, you won't bother to do such a thing.Why doesn't google tell us in our mail which problem we need to fix, to get our site approved by AdSense. They should be more direct. That would help a lot to be able to solve it quickly. I don't know which one should I fix in my website.. They are reviewing currently with less flow. I applied in this COVID 19 situation but rejected anyways.
When Google reject a site, They Should explain in detail why you have rejected it. We don't know which the problem we need to fix exactly!
I think the best thing would be that Adsense could give us a more detailed explanation of why a particular site is not approved, by sending URL's, details etc, since the system, finding any error, will have to block the approval. I don't think it's so complicated for Google, and it would help thousands of publishers to have approved sites also generating thousands of Adsense revenue