“This is the story of the revelation in late 2013 that Bitcoin was, in fact, the opposite of untraceable—that its blockchain would actually allow researchers, tech companies, and law enforcement to trace and identify users with even more transparency than the existing financial system.”
There’s a difference between “bitcoin is a public ledger” and “we can determine that Alice paid Bob 1 bitcoin”.
The bitcoin devs thought they could achieve the “public ledger” part while avoiding the second part. It turns out they couldn’t.