You're surprised that the handheld console with controller inputs, only really works well for games designed for....controller inputs? I don't really know how you expected anything different? Obviously playing games designed for keyboard/mouse is gonna have to make compromises to work on a device with controller inputs, it's the same way when playing games designed for controllers on PC. You either plug in a controller or deal with the (usually slight) jankiness. Same goes in reverse for the Deck.