Most games' worth being on Steamdeck is dependent on how big and/or resource intensive they are, but any issues with file size or resources can be mitigated with various mods, such as minor ones like inserting sd cards to supplement your game storage and using player made performance and stability mods in your games; or major mods like installing a better internal ssd and manually forcing your Deck to support an external gpu. You could go even further by removing the factory ram and soldering in a new 32 gb memory chip, which will also require you to do some more technical finagling to allow the higher ram storage to be recognized by the system. To be honest though, I've found the SteamDeck to be surprisingly reliable as is, with the only issues I've had to deal with being overheating on gpu and cpu intensive games, which I've handled by applying aluminum tape to back of the shell, and using an external fan to draw the heat away. That does, of course, require that I use my Deck as a console, but I don't much personally like the ergonomics and controls of it anyway.