Theorectically, people can understand impermanence when you ask them about it.
Practically, to internalize this is not easy, not done by many.
Those who realizes impermanence of all except Nibbāna should feel meaninglessness of living a lay life, be it discovering the theory of everything in physics, becoming more famous than Einstein, or producing kids and live on in the memories for maybe 3 more generations, or even saving the earth from global warming, or become superman, and save the whole universe, none of these achievements lasts, in the super long run of many universe cycles.
Not even getting good kamma, be reborn in the highest formless realms lasts. Those who see impermanence this deep has only one logical choice. To practise for the attainment of Nibbāna. Nothing else is worth it.
Another level is deep direct insight via meditation to break the unconscious clinging onto things which are impermanent.
Imagine if smartphones are as disposable as papers. We don’t cling to paper notes as we know that it disappears fast enough somehow. So if smartphones are as impermanent as papers, we wouldn’t cling to it. Or tissue paper even. Whatever is impermanent and clearly seen as such, we have no clinging to it. Thus a person who deeply, truly sees impermanence in all conditioned phenomena would let go of the all.
To get there, we have to meditate deeply, get a calm mind, fulfill all the noble 8fold path, practise Vipassana, reflection, learn the dhamma etc.