I think it's more that those gaming for spectacle are less invested in the overall outcome.
I can only speak for myself, but whilst I enjoy a win as much as the next nerd, as long as I feel I gave a good account of myself, I'll still enjoy the game I just played.
All games have their idiots who take the competitive angle far, far too seriously. X-Wing has Fortressing, where you perform no manoeuvres, let alone manoeuvres of spectacular cunning. You just park up from the outset, with a near 360 fire arc from your ships. How bloody boring must that be to fight? You've taken a pretty simplistic rules set (there's really very little to the rules), and you've managed to break it, because winning means that much to you.
I'm not terribly familiar with other games, but I suspect the same kind of idiocy can be done.
GW rules are arguably more open to abuse, but the cause and effect is the same. One player puts their precious win record over and above all else, making the game piss poor lame for their opponent. As a company, they've made the design choice to have as open a system as they can manage. Unbound, Allies, Random Charts - these are not decisions made when you're designing a game intended for strict play.
Another common factor used to bash GW rule sets? How long a game takes to play. What a bogus argument. It's a hobby game. When my mates and I get together for a Heresy game, it's played out over an evening, at a relaxed pace. That is how the designers designed it. Tournaments apparently require three or four games a day. So by introducing a time limit, you straight away shift what is going to work. Massive hordes of infantry? Probably not. Smallish squads in transports, perhaps half a dozen composite units to your army? Yeah, less to move, more effective dice rolling.