macOS doesn't require developers to rebuild apps with each major OS release, as long as they link with system libraries and don't try to (for example) directly make syscalls.

Apple may require rebuilds at some point for their Mac Store (or whatever they call it), but it's not required from a technical perspective.

The one exception here is CPU architecture changes, and even then, Apple has provided seamless emulation/translation layers that they keep around for quite a few years before dropping support.