And? the impact they left on the viewer is still there because when we were watching/reader we had no idea if the deaths were permanent. Freiza to this day is considered one of the most iconic shonen villains and everybody he killed is alive in the current story.
I know people give Oda shit for "nobody dies in One Piece", but is the alternative of "People die in One Piece, but then everyone gets revived with magic" much better?