Briefly informed: After Valve in March had already added the warning in the Steam Client Beta that support for Windows 7, 8 and 8.1, as well as for macOS 10.11 and 10.12 is ending, this has now been added to the final version as well.
With the update from 04/26/23, these older operating systems now show a notice that support will end on January 1, 2024.MacOS 10.11 and 10.12 will be available on September 1st, 2023.It’s been a while since Valve stopped supporting XP and Vista.But that is the passage of time.If you look at the numbers from March 2023, you can see that these operating systems are only rarely used.
Incidentally, corrections were also made, which you can see read here can.