Right. If you're going to question the commitment of a player, it's hardly unreasonable to expect a better supporting argument than some vague sentiment about what some ex-footballers might have said about players in general.
Luke Shaw has a history of injury problems. He has been one of our better performers in recent seasons when fit. It isn't in his interests to rule himself out of an entire season of club football when there is an international tournament on the horizon. He has already come out on social media denying the suggestions you're making. Do you really think he would've chosen not to play in the FA Cup final if there was any chance he could've been available to play in it?
If you're going to ignore all of that to peddle some conspiracy that he just doesn't want to play for United, I don't really know what kind of response you're expecting. I can't understand why anybody who purports to be a United fan would choose to buy into a theory with that level of toxicity when there is no evidence to support it.