Genetics isn’t almost everything. For big five traits overall it looks to be around 40-60%, with significant variance for some of the traits. Although there is good evidence of IQ being heritable at up to 80% (adults, not children), upbringing and social factors significantly mediate this effect. In ideal circumstances (e.g. good nutrition, stable household and social setting) heritability is in the higher end. In more challenged circumstances heritability drops.

I included personality along with IQ as both are strongly evidenced to affect outcomes.