Steam is a legitimate value add for sellers and buyers/users, that justifies its 30% cut. Other than free games, Epic has a seemingly easy-to-integrate online networking system, that’s about it. Steam has a modding platform, broadcasting, remote “parsec”-like controller emulator, Linux support, content sharing, forums and a developer news feed. That’s quite a lot.
What makes me stick with them is that they don’t preclude Steam and other gaming users from using alternatives but simply compete with their own well-made system… plenty of games have their own cross-platform mod-launchers that aren’t workshop for example. Steamworks DRM isn’t required and Steam networking services for multiplayer aren’t mandatory either.
That said, itch and GoG are great alternatives where they have games available. I’d just like GoG to provide better Linux support.