If you spend years working in an area of research, that activity starts to become its own little world. And like any human world, that world begins to develop its own language and culture.
A problem and then arise when you try to explain your work to others. From the perspective of many listeners, you are speaking an alien language. At best they try their best to understand that language. At worst, they are resentful of how your well meaning explanation is, in a sense, making them feel illiterate.
Which is why it is important to distinguish between the research and the demo. A demo does not try to explain things fully. Rather, it tries to communicate why what you have been working on is meaningful or important to others.
One of the hardest things to do in research is to separate yourself from all of those technical details that you are so proud of, and think about what you’ve been doing might mean to others. Once you can do that, you can start to design a great demo.