I remember following the guides to get OS X 10.3 installed on G3 machines...

What was the reason for that bug preventing OS X booting on older machines?

The reason was to force you into buying a new Mac. For example, the 2014 and 2015 rMBP are literally the same hardware. Same CPU, same GPU, same wifi chips. The only difference was one had a physical trackpad and the newer used a haptic trackpad. The last officially released OS for rMBP 2014 was MacOS 11, and rMBP 2015 was MacOS 12. There was nothing in the OS that prevented future OSes from running on a 5 year old Macbook except Apple didn't want it.

The 2014 models could have come with an nVidia GPU. They are not the same boards at all, which means that it's not just a "to hell with the 2014".

There's more to a computer than a spec sheet.

The most beautiful (as in "beautifully evil") aspect of it is that you don't need to do anything to make this "planned obsolescence" happen. You just develop stuff under time pressure (of course) while pretending those slightly older machines don't exist. So if an old driver gives you grief because it needs some find/replace work, you just don't care, you yank it wholesale.

Note that open source projects employ the same tactics. Act I: "oh, we made our thing compile in Wayland-only mode, but don't worry, you can still configure --with-x11". Act II: "Now that most distributions we think matter are shipping Wayland-only builds, we deprecate the X code". Act III: "Oh the --with-x11 started causing compilation errors or bugs, we decided to yank it off and also close all 22 MRs that were fixing these exact errors".

So, don't ascribe to malice what can be ascribed to CADT and budget cuts.

I won’t say I like this phenomenon in oss , but isn’t it a bit of what’s supposed to happen? ie if enough people care about certain code paths working , they pony up and make them work?