But are you planning to solve the problem, either with unity or by yourselves, or do you plan to ignore it?
You produce a game on a platform (recent Macs) where it runs only severely tamed, without any warning about that (at least none that I could find, neither in the system requirements nor where you discuss resolutions in the official game wiki). This could be acceptable only if you are actively working on a fix (and hoping to achieve it in a reasonable time), not if you just say is Someone Else's Problem, or fault.
At the very least, you should give to the ones who bought the game on the Mac app store a steam/gog code, so they could play the game on another platform, if possible.