Aside from certain pathological cases (gymnasts need to be short and thin, offensive linemen need to be freaky massive), the difference genetics makes is pretty small in the grand scheme of things compared to proper training and mindset. Definitely less than 10% of total performance (with the exact number depending on the specific sport). Of course, at the very top, 10% is often a bigger margin than between first and last place.

grandalf speaks of team sports and situational awareness, complex planning, reading the floor, and other mental aspects of sports.

The examples in the "Sports Gene" are mostly about the kind of genetics that allow some to run micro to milliseconds faster than others, oxygenate slightly better, and so on. These things might help in the olympics where such minor distinctions matter but are certainly not a key or deciding factor in many sports.