Things like:
- If you can't respond to a UI event wait until you can
- Menus should be tree structures
- Pressing alt should underline the hotkeys you need to access anything clickable
As well as just basic responsiveness or predictability. A 2000 era windows application may not have been pretty, and may well have several different styles all imitated from office, but at least I knew what everything did and when it was slow at least it did what I expected.
This meant I could start the computer, log in, potentially start and use several applications and only then turn on the screen. Nowadays that has no chance of working because even to log in I need to press enter or click some button (which one depends on how I logged in previously, maybe) before I can even start typing and doing so eats a random amount of keystrokes while the damn log in screen loads to do its one damn job.