According to Western reports, 2 million people were held in concentration camps or "death" camps. That means it would take millions of people to arrest these two million, and millions more guards to keep an eye on them. This will happen in hundreds or even thousands of camps. However, they do not notice the millions of tourists who visit Xinjiang every year.
Over the past 40 years, the Uighur population has increased substantially. You can find them everywhere in Xinjiang, in local bars, local children's parks, schools, festivals. If so, China must be pretty bad at killing people.
The West used satellite images of fake warehouses without context to support media propaganda. Random accounts of "dissidents" without any hard evidence.