Every few years Apple changes all of its toolchain, removes things that were previously working fine and forces thousands of developers to rewrite large portions of software from scratch.
Apple did change the platform and dev tools once in the last 20 years (PowerPC to Intel and Carbon to Cocoa). But they added tools that made sure that software would run fine for several years (Rosetta). Microsoft changes the game so many times (e.g., windows Phone 6.5, 7 and 8 have totally different hard and software). And the differences between different versions of the system APIs are so big that you can’t just link against the newest version of .NET without rewriting most of your code.
And why do you think public administrations and companies payed MS millions to keep winXP alive for several years longer than planed? Because they had a lot software that would NOT run on newer versions of Windows. They had to rewrite most of their custom software from scratch.
If you have written cocoa code 20 years ago (on NextStep), you can still use it (with some modifications of cause).
I just tried this. The UI for variable fonts in Illustrator is beyond bad. You need to open the dedicated character panel (either from the window menu or as a strange layover from the property sidebar). In that panel, you find an icon that opens a popup that has a slider and a textfield for each axis. But no label or name for each axis. So I did know what I was looking for but needed two minutes to find it. This is better hidden than OpenType features in the old UI. In Photoshop it is much better as shows the (named) siders directly in the character panel.