Physics simple?
Physical intuition?
The single most successful program of physics is quantum mechanics, and it is neither intuitive nor simple. Relativity, while conceptually simple, isn't so simple either and is far from intuitive (consider that momentum is conserved during a relativistic near-miss collision only if one considers the entire collision over a sufficiently length period, since at any moment the force vector between the bodies does NOT align with separation vector, since the force acting at one moment was exchanged, at c, when the bodies were in different positions).
There are a lot of simple concepts in physics, many of them basically teaching aids to get people started. When one gets deep into the field, simple and intuitive go by the wayside.