It all depends on how you want to play.
If someone wants to reject a casual MtG game because there opponent's deck isn't good enough then I'd strongly suggest they help that other player get better and get of their high horse. If you expect every deck you play against to be tournament quality and to use proxies if that is the only way to do so I'm pretty sure I wouldn't want to play with you. Of course in MtG I believe the power level in things swings far more than it does in X-Wing and in MtG the only "luck" involved is in what cards you draw and there is plenty you can do to control that.
I wonder what "motley collection of ships" one would need to face to think that their squadron is "too good" to risk being shown up by it? Maybe that collection is the undiscovered metagame breaker. Maybe the person behind it is good enough that they are just playing it because it's going to be a challenge. Heaven forbid that the game happens and the dice gods smile on the motley collection.