So what should a a 21st century UI look like?
If we are *still* using computer monitors, then the single worst part of UI design is to waste valuable vertical space with a title bar, menu, all the space below the user area. Design features from Windows 3. Maybe earlier, see below.
It also seems to be to be anachronistic to have a menu bar item labelled "Edit" which, with word processing apps does not let you edit the document. Although pretty much everything else in the menu bar is just as obsolete.
Next would be the silly notion of application names. I do not care what an app is called, I care about what it does! So I do not want something called LibreOffice - especially not with camel¹ case formatting - needless key presses for an idiotic (and inconsistent) way to show where words start, I want an icon that says: write stuff of something else, equally informative.
In fact, the whole idea of icons seems rather 1970s (from the 3 Rivers PERQ). All a UI should contain is a single question: what do you want to do? with a free-form field for the user to write (or say) their instruction. It should then be up to the smarts inside to decide how to fulfill that command.
It seems to me that the first steps to setting ourselves free of these out-dated ideas is to get rid of the limitations imposed by the traditional 2-button mouse and ASCII / 101-key keyboards.
[1] camel: a horse designed by committee. camelCase, just as dumb.