Whenever someone like Cam'ron, Clipse, Lil Wayne or Gucci Mane gets hyped as the new rapper(s) du jour, the same argument seems to keep popping up. They can't be great lyricists because they always rap about the same ignorant shit. They don't provide any significant insight into the topics they're dealing with. Etc., etc.
Now, this isn't really about my opinion on any of these guys. Personally I don't like the Gucci Mane I've heard and I'm not a huge fan of Cam or the Clipse. But the arguments generally made against these types of rappers don't seem to have much to do with their lyrical abilities or lack thereof.
Take Biggie's "Unbelievable" for example. Not his most meaningful song, but you could still point it out as an example of his lyrical talent. What's the difference between that and "Let the Beat Build," other than the latter being somewhat more scatterbrained in its approach? Both songs work not only because of the flow, but because of the lyrical imagery, wordplay and punchlines involved. The fact that there's no real cohesive narrative isn't really relevant.
Of course, when the aforementioned rappers get praised as brilliant, I understand why people tend to have a problem with it. There's the sense that some critics are reading too much into their lyrics, and putting rappers arguably promoting destructive stereotypes on some kind of pedestal. Both potentially valid points. But there's typically a lot more going on in a Lil Wayne song than one by Rick Ross, even if on the surface they might not be all that different. I'd rather read people try and maybe fail to articulate exactly what's appealing about such songs, instead of indiscriminately labeling them all as shallow party music not deserving of any critical analysis beyond that.
Ultimately, the fact of the matter is that some of these rappers have been hyped because they've done legitimately interesting things with lyrics and flow. How smart or stupid they are in real life is another discussion, and for the most part I don't think people are trying to elevate their music to poetry. It's just that it's entirely possible to be a great lyricist without rhyming about anything particularly important.