Engines are not just "hanged wherever one likes". There's an optimal point along the wing where airflow entering the engine will provide optimal performance, and it's not near the wing root.
It's pretty much a given that anything you read about aerodynamics on an Internet forum will be a massive generalization made to illustrate a simplified version of the point.
Look at the rubbish people keep on repeating about the reasons for inherent instability for a prime example!
