In fact, I occasionally run (currently maintained) CJK commercial software on my en-US Windows installation and I still run into ??? from time to time and have to guess what the text is supposed to be. It’s a shitshow.
True unification into Unicode only happened during the mobile shift in the form of iOS/Android.
It’s not as bad as trying to load some really old CJK web pages on mobile devices: few mobile browser has an accessible option to select character encoding and there appears to be none on iOS. The only option is to change the system language and that didn’t always work for more obscure character codes.