Anecdotal, maybe, but three of the apps I am currently running on this M1 Pro are quite old and work the same: Adium (last build almost 7 years ago), Slate (12 years ago), and Notational Velocity (13 years). Laptops go, but my .app bundles stay ;-).
...but any apps from 20 years ago like the Corel Draw example will have a nice "No" cross over them, as they'll be PowerPC (either Mac OS X or classic). 15 years old stuff will probably be a no go as well, as they'll largely be 32 bit x86. And frankly, most people expect 64 bit x86 support to go away sooner rather than later. Apple really are aggressive about this stuff.
The latest build of my software applications (built with Qt 5) work back to macOS 10.13, which was released in 2017. If your macOS is pre 10.13 they won't run.
I agree about Windows, though.