It's good for new games too! With Lutris I can even install Windows games with Proton on Linux, or choose my own Wine setup. I think Heroic Game Launcher does the same.

Best of all, no internet connection is required once a game is downloaded, unless the game specifically demands it. You can save your installers locally and keep them forever, never needing to phone home. If push comes to shove, install a VM of an old OS, and it'll run just the same. Connecting old OSes to the internet is potentially a security risk. And, as we see here, Steam ain't gonna work on old OSes anyway. You're going to need to pirate the games you already bought if you want to play them again in 20 years.

Okay, you just blew my mind. How does one download installers for DRM-free games on Steam? How do you even tell which games are DRM-free? I was not able to find answers with some quick searching, just community-maintained lists of games that are ostensibly DRM-free in one way or another. But how do I verify that? How do I archive installers?

The alternative to Chromium-based apps is not Gecko-based apps; it is native apps, that do not require an entire bloated web engine to run.

This is especially obnoxious with Steam since it wants to run in the background 24/7.