I might be wrong but I heard of bad performance in good computers as well in the case of Starfield.

So yeah Deck will always have issues with certain new AAA because like the switch has a performance level of older hardware. But not all new AAA require super hardware and also in PC there usually lots of settings official and non official to improve performance, usually in exchange of worse quality but sometimes fixing bugs that were slowing down the game unnecessary and without sideffects.