What is it about this battle theme that makes it so good? To me it's energetic, upbeat, fun, and the way the electric guitar melody changes pitch in some parts evokes distant feelings of romance, longing, and nostalgia.

It also has some nice soundfonts from Gen 7, notably it borrows from Alola's route 10's drum beats and trumpets.

https://youtu.be/lgtmXk1tyrQ