Dragon Ball doesn’t sideline only female characters. Like Android 18 was one of the main antagonists in the Cell Saga and was later brought back in the tournament of power. And characters like Tien, Krillin, and Yamcha were all sidelined after Goku became a Super Saiyan. And Bulma and Chi Chi are sidelined only because of their humanity and because of their lack of training. So Dragon Ball sidelines a fair share of both male and female characters.