I'm fairly sure this thread has happened before here.
Needless to say you guys nail the problems of challenging Steam.
GOG targets a different audience. DRM free and a community of nostalgia for the most part. They seem to try to nurture various social avenues for the nostalgia, with the forums and public wish lists. If their games and philosophy appeal to a person, then I think opinion changes.
Origin gives away free stuff. I have like 15 older games they gave away for free. Westwood collection, Wing Commanders, Jade Empire, SimCity games, and some others. Their program needs some work on GUI scaling.
Uplay is probably the least useful. Nothing special or positive about Ubi. I don't really like any ubisoft games so I don't use that much. It works as well as the others though.
Impulse/Gamestop imploded and just stopped working. That was bullshit and ironic after Stardock's philosophical gamer nonsense years earlier. Some Reddit guys figured out an old version of the program still at least could log on and so I could get the serials of the 3 games I had there and register them on Steam.