Pretty much everything really. It’s basically a store and that’s it, no cool features that Steam has. They may have achievements now but not positive. Think it took two years just for them to add a shopping cart. They dump money on developers to release exclusively on Epic instead of spending it making a good experience for customers. No reviews, no forums, no workshop etc.
I grab the free games they offer every couple weeks and use Heroic to play them, not touching their launcher.
Like most others said. Dead Cells and Binding of Isaac are the top dogs. No matter what else I play I always circle back to one of those two eventually and get sucked in again. But some other lesser known ones that are good are:
Cursed to Golf - 2d golfing roguelike, no combat or anything. There’s a bunch of different cards to make the ball do different stuff. From a rocket ball you control after hitting to an ice ball that’ll freeze water hazards to a drill so you can tunnel through walls.
Oblivion Override - 2d with fast combat and a lot of perks and weapons that change things up. Perks from different “trees” have synergies that are a lot of fun.
Rogue Prince of Persia - 2d parkour style combat made by the folks that did most of Dead Cells post launch updates, still in early access but still fun.
Soundfall - not a true roguelike, top down rhythm shooter with random loot.
BlazBlue Entropy Effect - 2d with a boatload of different classes, different elemental perks that synergize and each class has different perks to add new melee combos
Curse of the Dead Gods - isometric with slower parry based combat, has some mechanics with light and dark that some folks don’t like. If there isn’t a light source nearby you can’t see traps and take extra damage but you can pull a torch out to light braziers or enemies on fire to illuminate the area.
Ravenswatch - same people that made Curse of the Dead Gods. Isometric with different classes and online co-op.
Voidigo - top down shooter with unique art and sound design. Lot of weapons and four or five different characters with unique abilities.
Have a Nice Death - 2d melee with nice movement, mechanics don’t seem as deep as others but still fun.
Dandy Ace - isometric with ranged combat. Magician that throws cards around, good selection of abilities.
Patch Quest - top down, hard to explain this one, might wanna watch a video to see how it plays.
Devil Slayer Raksasi - top down with a lot of elemental effects. Haven’t spent much time with it though.
Well this got a bit longer than I meant but they’re all solid, not sure if they’re all on Switch though.
One more, not a roguelike at all but Switch exclusive and a surprisingly awesome game. Golf Story, check it out.