How is this movie only 6.4/10?

Indeed, it's an excellent film. However, it got lost in the shadow of the very glossy (and gloomier) SE7EN. Films are much more music video-like now. By contrast, what I loved about COPYCAT was it's subtle terror that creeped up on you. The movie is filmed very much like an upper-class horror film but it's also intelligent.
It astonishes me when great films get overlooked. COPYCAT is one of those. It's still a smashing film that has lost none of its effect 11 years later. In fact - the story is STILL relevant today. As Sigourney's character says earlier in the film about there seeming to be more and more serial killers...well, our society is getting scarier and scarier.
The fantastic and unrealistic (although clever and well-constructed) SE7EN just doesn't frighten me the way COPYCAT and SILENCE OF THE LAMBS do. They seem very grounded in the reality of our world. Scary stuff indeed - especially when the killer seems the most least likely to be one!