I love the fact that on the games requirements on the Steam page it still says it runs on Windows XP when in fact all support has been cut for long now, leaving out many of us who got into Steam on the first place because we either wanted a legal digital copy of our physical collection or because many physical game keys WOULD also activate a digital license. I still keep Windows 8 because it's still supported on Stea…
Steam uses Chrome for its web integration. They * can't* support OS's that Chrome doesn't anymore If you already own the game though arguably it's not unreasonable to download a "NOSTEAM" torrent (if any still exist) of the relevant game you'd want to play on your XP rig
They CAN choose NOT to use Chrome. They used Windows' browser before and no browser component before that. Steam doesn't NEED an embedded browser, having one just makes things more convenient for Valve because they can reuse their website in the client.
They CAN maintain support for older versions in their fork of Chrome. Browsers are expansive but not rocket science. Valve has the funds to maintain one.
They CAN make a specced down version of Steam (or GUI for steamcmd) for older operating systems. They don't have to keep selling Games on older operating systems (or could require an external browser for that) but taking away the ability to run already sold ones is unacceptable.
Problems caused by middleware are still the responsibility of the developer using that middleware. The end user does not and should not have to care how you cobble together your software.
They have simply decided that doing the right thing would be more costly than whatever cost they will incur from dropping support. That only works out for them because people accept this shit rather than demanding Valve keep their promise that you can continue to play the games you bought from them without trying to add additional conditions.