Steam only being 32-bit isn’t improving compatibility, it’s being lazy. You can write code that works on both architectures for the best performance and compatibility across all PCs, like Chrome, Firefox, MS Office, etc.

Every other major application and service on Mac has ARM-native builds now, there’s not really an excuse for Valve. It’s especially silly when much of Steam is running through a Chromium engine, not machine code or anything else that might be difficult to port.

There’s a difference between Valve deciding to not make Mac games anymore and Valve leaving the Mac Steam client a slow and laggy mess on newer Macs. The former only affects people who want to play Valve games, the latter affects a lot more people.