That's true and it's kind of sad. It's really unfortunate that Perfect Dark did not sell more. It should have been more influential than it was.
According to someone at Rare, it sold around 3.2 million copies. Other figures put it at 2.5, but Rare probably know better. That was less than half of what GE sold, but was pretty huge by FPS standards of the time. Especially since PD was released in mid-2000 and the system's life cycle was mostly wrapped up by late 2001. GE had the benefit of selling throughout 1997-2001.
Perfect Dark's influence is difficult to separate from GoldenEye's. It's like trying to distinguish between Crysis and Crysis 2's influence on gaming. You can find their influence in a lot of places, but a lot of what Crysis 2 did was already present in Crysis.
On a slightly different topic, one of the developers from GoldenEye: Source is currently working on a remake of GoldenEye for PC, aiming for release in 2022.
Even David Doak has chimed in with his opinions on the project.
This project looks very promising, and I'm a little wary about MS/Nintendo reviving GoldenEye XBLA and finding reason to try and squash the project. To date, there have been no legal challenges against stuff like GoldenEye: Source, but that could change.