In my view this article was really informative, providing all the right facts and points needed to understand the concept scientifically. 

Not every child learns at the same pace and obviously there are a few gifted geniuses who just do better than you no matter how hard working you are.

We humans need to normalise it ,even though all these factors may influence a child's learning skills but even if everything is right still they may not perform well. 

Well ..to simply it, it's like asking a fish to climb a tree or a monkey to swim underwater because obviously ,a fish can swim better whereas a monkey can climb a tree better. Everyone is different. Accept and appreciate the differences.

What are your views?

https://buddingpsychologists.org/factors-influencing-learning-in-children/