I think they really refer to the feeling it gives off. Like that uplay client you are forced to use even though you bought the Ubisoft game on steam. Epic just feels like a ball and chain.
Maybe it has changed to better. I don't have Epic Games, but a few years ago I went to a friend's home and tested Epic Games and it forced you to stay online in order to be able to play. There was no offline mode like in Steam.
I also have a subjective view. I really love the steam communities (uninvolved with Steam), workshop, Proton, Gamer communities. I feel that the approach of selling free candies that Epic Games has used it's untrustworthy. And Epic Games communities look. All friends that I know that have Epic Games it's because of the free candies, but nothing else. They don't open Epic Games for anything else, they don't talk on communities, etc.
Both of them are companies, but it feels like steam cares more about its community and users.
I personally have a launcher so things are neat and tidy instead of having a bunch of shortcuts on my desktop, that's all, I never use the community features and wish I didn't have to rely on a launcher for them when I need them. I much prefer finding answers to my questions on Gamefaqs forums than on Steam's (because I find their forum works like crap).