As a Mac user, I get that there won't be as many games available compared to what a PC gets. I accept that. Yet, Warcraft II was released on Mac back in the day. I'm confused why Blizzard and GOG don't have a Mac version on GOG. I wouldn't think it would be too difficult to port, would it?
It would be a lot of work for GOG, as the old Mac version was for classic Mac OS (Mac OS 9 and earlier) which is a completely different OS than what MacOS X and above is. The Battle.net Edition was also only built for the PPC architecture, which Apple dumped almost two decades ago. The amount of time to re-tool the game for modern Mac OS just probably wouldn't be worth their time.
The only solution is the one above where they are just running the game in an application layer like Wine or run Windows or classic MacOS in an emulator/virtual machine on the Mac.
Windows can get away with it because Microsoft builds on top of their old OS's each year and maintains compatibility for things years (and even decades) after release because customers and business demand compatibility for years.