The only problems I've had with Steam over the past several years in terms of flow from installing to playing games daily - is related to product in testing that is not released.
Steam has been pretty fucking flawless for installing, playing, updating etc, and I'm in the beta client.
Plenty of things for Steam to improve upon, but we hold it to a much higher standard in consideration of how immensely far ahead they are, and how it is being used as a primary PC games platform.
GOG has been good except for poor updating vs other platforms, poor curation policies from time to time and their beta client Galaxy is too resource heavy at the moment. But game installation and playing is no problem.
Can't say much good about EGS, Bethnet and Xbox Store/Gamepass, which have consistently been problematic