I think the point is not that GWAS can do everything, but that many people 5-10 years ago thought that they had a fundamental flaw - where was all the heritabil

I think the point is not that GWAS can do everything, but that many people 5-10 years ago thought that they had a fundamental flaw - where was all the heritability? It has turned out so far that the heritability is there and discoverable with big enough sample sizes. But of course, you are right that GWAS don't tell us much about the very large space between strands of DNA and social or behavioural outcomes. They are a tool like others. (Mendelian randomization is hardly a panacea - how credible are those exclusion restrictions, usually?)