Out of curiosity, I just checked, and while the CS6 installer is 32-bit, Photoshop CS6, at least, is 64-bit.
The .app icon shows the "circle slash" overlay, however, and attempting to launch it from the Finder (Sequoia 15.1 running on an Intel Mac) yields the OS-level "needs to be updated" alert without actually exec'ing the binary.
The Mach-O executable in "Contents/MacOS" loads and runs successfully when called directly from a shell prompt, however, and displays an application-generated "Some of the application components are missing…Please reinstall…" alert.
Which is actually encouraging, given that I'm attempting to run it directly from the Master Collection .dmg image without actually installing anything, which, given all the prerequisite detritus Adobe apps habitually scatter around the system when installed, I wouldn't expect to work even on a supported OS.
Less encouraging is the fact that the app-generated alert box text is blurry, suggesting the application wouldn't properly support Retina displays even if it could be cajoled into running.
Interesting experiment, thanks for the detail, I think I do still have my installers backed up somewhere, if not the actual disks.
> Less encouraging is the fact that the app-generated alert box text is blurry, suggesting the application wouldn't properly support Retina displays even if it could be cajoled into running.
This was actually the main reason I simply stopped using it (aside from not needing it professionally anymore and Adobe switching to subscription after CS6). CS6 was the last version before laptops started shipping with high dpi screens, and Carbon (from what I understood at the time) was simply the older cocoa UI framework that was replaced as Apple switched to a more versatile SDK. Sibling commentor suggested it was because Carbon was 32-bit only and that seems plausible, I hadn't experimented heavily with Obj-C or Apple dev, but I'm sure the switch was a massive undertaking.
64-bit Carbon (as a port of 32-bit Carbon, which itself was an aid for porting apps from classic Mac OS to OS X) was originally loudly announced and then relatively quietly killed[1]. Not clear if any code was ever actually written, but given the announcement was at a keynote I expect that somebody, somewhere, at least judged it feasible.
[1] https://www.macrumors.com/2007/06/13/leopard-drops-carbon-64...
CS6 is after the Carbon2Cocoa effort, IIRC. No 32bit apps run on modern macOS and Carbon was infamously 32bit only.