We've lost some common features:
* Undo & redo
* Help files & context sensitive F1
* Hints on mouse hover
* Keyboard shortcuts & shortcut customisation
* Main menus
* Files & directories
* ESC to close/back
* Drag n drop
Revelation features when they first became common. Now mostly gone on mobile and websites.
Also having the cursor show up in the proper place on a new form and having tab order work.
And knowing how to get the version of an application (which used to be in Help -> About).