This doesn't really pass the sniff test; if there were any easy one-gene changes that resulted in unambiguously better results, it's highly likely that we'd all have them already.
Well, these aren't unambiguously "better results", not in a biological sense. Just better in terms of what our culture values, and not necessarily better survival and reproduction.
BCRA mutations: "It’s estimated that 55 – 65% of women with the BRCA1 mutation will develop breast cancer before age 70" [0]
ApoE4: "individuals with two versions of the ApoE 4 gene have a 50% chance of developing Alzheimer’s" [1]
HTT: The Huntingtons gene. If you have the wrong version of this gene, you will get Huntington' disease.
All that to say that, in these cases, sure _most_ people have positive traits from these genes, not all do and we could theoretically use CRISPR to change people with the negative versions of these genes to the positive versions of these genes.
