Prior to full-screen mode on macOS, you would option-click the window resize button to resize it to the full size of the screen. This still works. It just doesn’t snap.
Option-click maximizes to full screen minus menu bar and desktop volume icons.
Apps like games and screen savers don't seem top have trouble covering up the entire desktop and menu bar.
I prefer it to the current macOS Finder where zooming covers up the menu bar and desktop volume icons, and where there doesn't seem to be an easy way to zoom to content.
