Fohat, a society can not function, if every person born is of equal intelligence, equal compassion, equal physical strength, equally good looking, etc.
A society, requires control mechanisms, it requires muscles, it requires transport, it requires expendable soldiers that take orders without much thought of their own, JUST as a single human body is not composed of cells of the same type.
There are different classes of humans, this is just a fact of life, but there is not as you say, Cockroach class. The less-minding class are a necessary and valid existence, if not for them in significantly greater numbers than bookish-humans, society could not be built..
The gene pool is optimal as is, you may assume that Today's-masters-of-this-world have the best genes, this couldn't be further from the truth, they have the Controller Genes, and they assume/gravitate towards their societal role/ destiny.
Remember, there is SEXUAL-selection, and there is NATURAL-selection. Natural selection is macro-scale long term adaptation, Sexual selection is rapid radical changes.
If it was as you say, the smarter the human the better, the smarter the animals the better, Very quickly, within 10 generations, all humans and all animals would be significantly smarter than 1st gen. And yet there is no indication of this. If anything, the distributions in intelligence has mostly stayed the same.
This means, nature actively selects AGAINST intelligence to a degree, WHY does it do this. That's from natural selection. We are not all supposed to be the same, and we have our own DIVERSE biological destiny/role to fulfill.
As for whether some humans are "too lazy" to have children. Probably, but again, this is genetic destiny. Nature has a programming, it says, Under ABXY-circumstances, do not feel compelled to procreate.
We are in those circumstances Today.