Those benchmarks are for CPU-bound tasks. Typical web sites usually have other kinds of bottlenecks.

So, if you're doing heavy calculations in your user interface layer (that's what a web site is) - you're a) supposedly doing something wrong b) probably better with something else than plain CPython.

In many other cases, Python is fine. Not the very best option, performance-wise, but there are many other aspects than performance, too.