Steam exists on macOS, but honestly it feels like a second class citizen to me. Lots of the games that used to work fine no longer work because they are 32-bit and are no longer supported on current macOS releases, which only support 64-bit binaries. We can argue back and forth all day about whether this is Apple’s fault or the developers’ fault, but a key giveaway to me is that Portal and Portal 2, which are (arguably at least) flagship games for Valve, have not have 64-but releases. I get that it’s not as simple as a recompile & release, but to my mind it’s a bit of a giveaway that macOS doesn’t seem to have enough gaming market share to force a re-release on 64-bit for all these games.