I think the inclusion/relevance of impermanence and non-self are in how we interpret/follow the 8 Fold Path.
Although all eight spokes of the wheel depend on each other, Rght View/Right Understanding is where these topics rise to the surface as far as I can tell. One problem there is when people disagree because clinging to our idea of Right View/Understanding is to then miss it.
@Shoshin1 said:
Dukkha, suffering or dissatisfaction, is among the most misunderstood ideas in Buddhism. Life is dukkha, the Buddha said, but he didn’t mean that it is all unhappiness and disappointment. Rather, he meant that ultimately it cannot satisfy. Even when things do satisfy―a pleasant time with friends, a wonderful meal, a new car―the satisfaction doesn’t last because all things are impermanent.
Isn't it funny though? We can find the most comfy, cozy and satisfying position possible and after a while, no matter how comfortable we were, we will find ourselves in discomfort.
Just imagine how uncomfortable it would be if we didn't change while everything else did.