I'm not sure what it is about this video I don't like. It just didn't seem very much like a 3B1B video for some reason. Maybe it's because there were fewer "A HA" moments than in other videos. Maybe its the source material. Just feels...different.
Not sure why you did not have any "Aha" moment, bu the visual explanation used for the principle of superposition and approximation of functions by Fourier series is very informative. I also liked the explanation about the proportional relation between temperature and space in the heat equation. I think in most higher educational systems, they only approach this type of problems with pure theoretical solutions/explanations.