Epic isn't able to compete because their launcher is missing major simple features like reviews.
I don't want multiple extra steps when I'm interested in a game. Steam has a big market share because they are giving people what they want in a launcher. That's it.
Epic can put in the effort if they want but it's already been like 2 years and as far as i can tell hasn't really been updated with anything new, I use it for the free games sometimes but otherwise not really. That would only change if they make the launcher more attractive.