Mobile I give you -- of course that is obvious, it would be hard to get worse UI on a 1080p OLED screen that we had on a 50x100 pixel monochrome display.
Desktop, no way. Windows 2000/Office 2002 usability by beginners was head and shoulder above today's versions, even at 10x less dev effort and 100x less HD/RAM/CPU usage (yes the functionality was lesser, but the UI wasn't).
And add to that the counterfactual of 200,000 man years of development within sane UI paradigms that don't live under the pretense that every Windows PC is a touchscreen tablet, and you could have so much more!
90s UIs had clear guidelines and concepts - many apps did not follow them but there were references like Apple’s Human Interface Guidelines telling everyone the conventions and when to use them.
When we entered the “an artist designed everything in Flash” era and its successor flat design we saw a big hit to discoverability (I still routinely witness people being amazed at core app functions existing because they hadn’t realized that plain black text was a button, etc.) and some specific usability hits which disproportionately affect certain users: click targets requiring very high precision, lack of or inconsistent keyboard navigation and shortcuts, contrast/color/size choices which are hard for many people to read.
iOS is interesting for the degree to which you can re-enable functionality but non default options definitely get less testing.
Desktop, no way. Windows 2000/Office 2002 usability by beginners was head and shoulder above today's versions, even at 10x less dev effort and 100x less HD/RAM/CPU usage (yes the functionality was lesser, but the UI wasn't).
And add to that the counterfactual of 200,000 man years of development within sane UI paradigms that don't live under the pretense that every Windows PC is a touchscreen tablet, and you could have so much more!