Matched is pretty much the Cassia Reyes Story, and everything we see of the world (okay, the Society) is through her eyes. This means we've got front row seats for her progression from thinking Society is totally awesome to not-so-great for some folks to generally terrible and oppressive.
While it's fascinating to watch Cassia's transformation, most of us grew up in places not at all like the Society, so we think we speak for most readers when we say that we were suspicious of the Society's supposed perfection long before Cassia was. Which, of course, leads to moments when we're like "No! Don't do that!" and "Don't believe what they're telling you!"… What, you don't yell aloud to fictional book characters? Ahem, neither do we, of course.
Not only is Matched told solely through Cassia's eyes, it's also told in the present tense—for instance, "My heart stops, and I can't believe what I see" (3.69)—so we're not only in Cassia's head, we're bouncing around in there as she's making discoveries and falling in love and questioning her beliefs. So just like Cassia as she's experiencing these things, we don't have the benefit of 20/20 hindsight on events. The upshot of this is that we get to hear how Cassia feels about everything as she feels it, not as she might rationalize it later on.