I’m have the same problem and I try to fix it.
Now wc3 use metal on macOS by default, to run game on olden mac need to set run flag
-graphicsapi OpenGL
To automate this process I write simple shell script, you can download it by link yadi.sk/d/jBm6XRcINtnqiQ
Simple unpack zip archive and run app inside this.
NOTE: before run you need to instal wc3 from blizzard app launcher.