Why haven't ugly and dumb people been eliminated be evolution ? Why do they still exist despite Charles Darwin theory of natural selection.
As long as there is variation on the traits you mention, there will be one person to call those at the low extreme of the spectrum dumb or ugly. This would be true even if the average IQ was around 200. So the question really does not make much sense!
One will note that directional selection reduces genetic variance but this is quite clearly not what the OP had in mind so let's not go down this path.
On top of that you are assuming that these traits are under selection. Typically, you are assuming that higher intelligence is necessarily beneficial which might very much turn out to be wrong. As a start you can have a look at the wikipedia article on the Flynn effect or this Skeptics.SE post.
You talk about "Charles Darwin theory of natural selection" please note that our understanding of evolutionary processes is much more advanced today than Darwin's understanding. We call our theory of evolution the modern evolutionary synthesis. If you are curious to know a thing or two about what this theory says, you can have a look at Understanding Evolution for example, a free and short online introductory course to evolutionary biology from UC Berkeley.