It's not unfair in the sense of what he values in his films though. I don't think Bay is necessarily a bad filmmaker. The man knows how to create spectacle like none other. His characters suck but no one can front on how he constructs a scene or makes logical action scenes. Dialogue and nuance aren't his strengths. I'd say Snyder is closer to that than to someone who can pull off both nuance, great dialogue, and make the character scenes as dope as his action scenes. That's not to say he's not a bright dude because I can't imagine he can do what he does behind the camera and be dumb, but he's never been a guy who's focus starts with the emotion of the character or the arc or the scene and when he does focus on that stuff, the results are mixed. Everyone has their strengths. Action scenes are most certainly his strength. And set design and costuming and also making sure the music is right.
Some filmmakers want to appeal to your brain, some to your heart, some to your gut. Snyder is definitely a gut guy. And when you've got a bunch of film students reviewing your movies, sometimes the gut thing doesn't work for them. Unless its horror, which is probably why his Dawn of the Dead remake is his best critically reviewed flick