GD has always been designed as a "Rage Game" and not a "Rhythm Game".
Sure, some level creators care enough that they want to make sure that their levels are properly synced with the song, but even then you can't really get it to be synced perfectly, since the level editor itself has limitations, and if the player taps out of sync just once, it might break the entire level's sync, hinting that the editor itself wasn't really intended to follow the music accurately every beat like osu!'s editor does.
Yes. It requires you to listen to music to get down timings and complete levels. Many maps go with the beat to the music and so will you to to the beat of the music.