That site’s number of 31,000 tracked objects seems reasonably consistent with other sites. They really need to track as much as they physically can, because anything could cause a collision and damage.
https://aerospace.org/space-debris
I think what the CARA people are talking about is that they’re responsible for avoiding problems caused by NASA’s assets in space. They worry about other people’s stuff, but they’re not the ones who can do anything about that stuff. Each space launching entity is responsible for their own stuff.