This is the forum for the mobile app Adobe Color, not Photoshop. However, the paint bucket is not the best tool, never was. If an area is selected, you can use Command/Control + Delete to fill with the background color, and Option/Alt + Delete to fill with the foreground color. Because it is a selection, you can use the Refine Edge dialog (in the Control/Options Bar at the top of the application) to control how it fills around the edges.
Hope that helps.