Epic Store is light years behind Steam. It is very barebones and primitive. In Steam when you go to the games in your library you see a lot of content, you see your DLCS, achievements, community content, etc. In Epic Store you don't even have a page for each game in your library, just a small cover to launch the game. Steam has Play on TV, Play on phone/table and Remote Play together which are great features. Also Epic catalog is so much smaller than Steam's.

Also, it is interesting to have some context of Epic Games. I remember when it was Epic MegaGames and they released the original Unreal games, THAT was the hit that defined the company as they also started to license their Unreal Engine (which they still do today).

Long story short, around 2012 the massive chinese giant Tencent acquired a big portion of Epic Games (40%) that allows Tencent to nominate directors, and the company shifted towards GaaS (Game as a Service). Many long time Epic Game employees left the company around that time.

Epic Games used one of their games, Fortnite: Save the World, to develop Fortnite Battle Royale, which was a huge success.

It's very important to note that Fortnite's biggest competitor, PlayerUnkown's Battlegrounds (PUBG), is owned and developed by Tencent.

Also note that Tencent owns 100% of Riot Games, as well as having various stakes at different gaming studios.