I suppose the the initial post refers to Windows-style task bar that enumerates currently opened windows at the bottom of screen using list of buttons with application icons.
Gnome Shell interface is just not compatible with a workflow when one uses a lot of opened windows and actively working on few of them from different or same applications.
In the overview mode the windows becoming tiny rectangles that one cannot recognize. This is not the case with the task bar that uses always recognizable icons and window titles allowing navigate with 20 or more opened windows even if they come from the same application.
Using Alt-Tab and Alt-KeyAboveTab puts extra cognitive load as one has to constantly remember if the window the person wants to access belongs to the same application as current one or different one. Just consider switching between 2 browser windows and an editor.