Apple took the basic concept of a GUI and mouse-driven interface from Xerox, but the Lisa/Mac are far from a direct copy of what was demoed at PARC. Smalltalk didn't have a file browser, didn't have pull-down menus, didn't have desktop icons. It didn't even have window controls. If you wanted to move a window, you had to click on the window title, then select "move" from the pop-up menu, then click where you wanted the window to move to.

Besides just the graphical UI, Apple also implemented a lot of novel technical concepts. For example, Smalltalk windows couldn't redraw themselves when they were partially obscured. Apple didn't know this restriction existed, so Bill Atkinson in their Lisa group invented regions as a way to let partially obscured windows only repaint portions of themselves. Meanwhile Xerox's own solution for this restriction for the Star (their commercialized version of the GUI research) was to ban windows from overlapping at all.

Overall modern desktop GUIs have much more in common with the Lisa/Mac than the Lisa/Mac have in common with Smalltalk.