While you might be able to troubleshoot and fix your VirtualBox setup, there is another alternative that may work for you.
Wine is available for the Mac.
Wine (originally an acronym for "Wine Is Not an Emulator") is a compatibility layer capable of running Windows applications on several POSIX-compliant operating systems, such as Linux, macOS, & BSD. Instead of simulating internal Windows logic like a virtual machine or emulator, Wine translates Windows API calls into POSIX calls on-the-fly, eliminating the performance and memory penalties of other methods and allowing you to cleanly integrate Windows applications into your desktop.
Simply put, Wine lets you run Windows programs on non-Windows operating systems. Be aware that it is not always capable of doing so. Software run under Wine will have varying degrees of success. This can range from working perfectly, to not at all, and everywhere in between.
According to WineDB, Age of Mythology has a gold status, which is a high level of compatibility. Note that those tests were with older versions of Wine and the results might be better, worse, or the same under a different version.
Simply put, there is no harm in trying it under Wine, it may very well run perfectly, or well enough. If it doesnt, you can report your finding to WineDB. They may even try to fix the issue. Worst case, just delete it and try something else.