I'm not a PC gamer. Could someone explain to me why people hate EGS? What's wrong?
Firstly, understand that when people talk about steam, and the epic game store, they're actually talking about two different things at the exact same time. It's confusing to people who don't intimately understand technology, but these things, launchers are some call them, are a combination of store front, and technology suite. I'm sure you've heard of things like OpenGL or DirectX, those are technologies that help make games, specifically those technologies are middlewares that drive graphics cards. They make up a standard language so a game developer can target a "virtual" openGL or directX card, and the people behind OpenGL and DirectX (Khronos and Microsoft) then take care of making their "virtual" card work with physical cards. So from the perspective of a developer, you write for one "virtual" card, and the makers of that "virtual" card spend lots of money making it work with lots of real, physical cards. This is called interfacing.
Steam, the client, has a store bundled with it, but it is also a suite of tools. Steam, the client, can be thought of like DirectX, it does lots and lots of things beyond merely selling you the game. For example, there is this thing called Steam Proton which is an automatic translation layer for linux. With steam proton, you can run any windows game in linux, something thought absolutely impossible years ago. Steam is brimming with technologies like this, like Steam Input, which is how things like Dual Shock Controllers work.
You don't have to buy from Steam, the store, to use Steam, the client's tools. When you buy a game from, like, amazon, the sale goes entirely through amazon, and valve doesn't take 30% because they didn't actually facilitate the sale. But when you buy that game from amazon, or target.com, or where ever, they give you a special "installer" that you can pop into the steam client, and it'll use all the steam client features.
The Epic Games Store is, like the steam client, both a store and a suite of tools. But as a suite of tools, it's anemic. Not a fraction of what steam, the client, does. But worse than that, Epic is relying on people's confusion and inability to understand the difference between a store front and a suite of tools to muddy the picture. Were, for example, Epic Game Store just selling Steam Client installers, like Uplay does, nobody would have a fucking problem at all. But they don't. Instead, when something is "epic store exclusive," that means epic paid to both keep the game off of Valve's technology suite, AND keep it off of every other store besides their own. When something uses steam's technology, they are NOT exclusive to steam, the store. But people who don't know the difference think everything using steam's technology is the same as being exclusive to steam, the store.
By making things exclusive to epic games store, not only are they limiting the number of places where a buyer can purchase from (which has the demonstrable effect of raising game prices), it also cuts features from certain games by keeping them from using steam technologies.
In short, when things go "Epic games store" exclusive, they are limiting the places one can buy from, limiting the feature set of said, usually raising the price of said game, for absolutely no benefit to the consumer at all.
And, as an indie developer, Epic itself creates this division between games it allows onto the store, and games it does not. For games that are not allowed onto the store, it creates an unfair stigma, like those games are somehow lesser games, that actually hurts bottom lines. I don't want to use a specific example by name, because the specific dev got harassed when they made this known, but there was a well known, well reviewed game on steam that got denied a spot on epic game store, and after it got denied, the narrative on twitter turned into "something must clearly be wrong with the game if it got denied a spot on the store" and their sales actually slumped. One of the best features of steam, the store, from the perspective of small developers, is that it puts everyone on equal footing. A dude in bedroom can make a game and it's sold right alongside games made by 1000 person studios with million dollar budgets as though they were equals. EGS creates a division of haves vs have nots that hurt small developers.
EGS is bad for PC gaming all around.