The last time Blizzard patched the game, the latest operating systems were Windows 7 and OSX 10.7 Lion. As such, the game wouldn't even run on later OSX versions, and had issues on Windows 8 and up.

Diablo II should be easier to run on Windows 10 and Intel Macs, thanks to a patch from Blizzard. The game was first released in 2000, an eternity ago.