Even as a normal human with good motor control, good equipment, and decent eyesight, I routinely encounter situations (macOS) where I have to carefully move the pointer back and forth across a region where I know the "line" (divider, border) is so I get the opportunity to move something.
Another related problem is the overloading of the title bar. In the past, the title bar was always there for each window. Grabbing and moving a window was very easy. Now, many apps try to move menus and other controls into that space, leaving the user to find the few pixels here or there which can be grabbed to move the window (rather than taking some action within the app). Some apps allow you to revert to normal title bar (thank you Firefox), but some don't. And true, you gain some valuable screen space from what would normally be a wasted big area of title bar, but the tradeoff sucks when you need to move something.