As rhe name suggests, one of the big selling point of the Switch is that you can play it either handheld or docked, like a console. While you will be able to dock a Steam Deck too, that basically ends you up with a $399 PC; and PC gamers are terrible snobs, who will tell you that they have graphics cards more expensive than that. Most people buying a Steam Deck will never dock it, because they already got a more powerful PC. The reason to buy a Steam Deck is playing PC games handheld. I can think of a number of games for which that should work fine, especially indie games. I can also think of a lot of games that I sure as hell would not want to play on a 7” 1280x720 screen using thumb controllers. UI elements that have been designed to be readable on a 27” screen don’t necessarily scale down very well. And a thumbstick doesn’t have the same precision as a mouse. I’m not saying you can’t make great games for small screens and thumbsticks, but it is hard to make a game that is great on every possible screen size with every possible control setup. PC games aren’t usually designed for touch screen controls, for example.

There are some Switch games I don’t like, because they are basically ports of PC games and suffer from exactly these issues. And there are games on Steam, e.g. Monster Hunter Stories 2, which have been designed for a console and will run fine on the Steam Deck. But with my preference for relatively complicated games, I don’t think my Steam library would be a very good fit with the Steam Deck.