This isn’t a monopoly issue. Other launchers exist. Most of the games on Steam are available on these other launcher, yet people still prefer Steam.
I can only speak for myself, but I prefer Steam because it’s more customizable so I can set it to open to my library first instead of a rotating ad banner, the storefront ads are not intrusive and can be easily ignored, and steams remote play is something that no other launcher offers.
In fact, I am not sure what the other launchers offer that they excel at over Steam.
The reason players prefer Steam is because the other products are not good. If a launcher wants to compete with Steam, they need to do things that Steam does better than Steam or do things that Steam cannot do yet. Right now, I log into Steam and I am immediately in my library without any ads or recommendations, ready to launch because Steam lets me pick where I load in. When I log into Epic, I am stuck in the store page with a full app rotating banner of a bunch of games I am not interested in. Plus the library is limited in scope and I have to slowly navigate through all the games to find the game I want to play. Same with Blizzard, Ubi, all of them.
I don’t know if you intended it this way, but saying that Steam users are hostile of other launchers makes us sound like we are unreasonable in what we are asking for. If Epic was better than Steam, I would use it. It’s not.