New Kaguya ED is just another way of showing how the staff are big BIG fans of the source material. You can pick up so many references that take place in future events. Even as an anime only, you can appreciate the drawings.
When I first read it years ago, I wondered what it'd look like animated. I was happy enough with S1, but to know that they absolutely care about the source material fills me with hope (and anxiety lol) of how it'll turn out