For me it's not about fortnite but more about fast-paced multiplayer on the steam deck
When I played Rocket league on the deck instead of my Desktop with Lan, higher resolution and much higher framerate I always felt as if I'm playing much worse than I usually do which is not fun in the slightest
It's a great console for singleplayer and more tactical multiplayer but whenever reading the screen in less than a second and reacting very fast to it in an online game is necessary that's not great...