While rap music began with predominantly simplistic rhyme scheme couplets, it has progressed into something as creative and as diverse as the many rappers that we have today. Although the rhyme schemes were basic, the music as a whole was not-- N.W.A. always managed to tell a story even if they used simpler rhyme schemes and flows, often with two end rhymes in a couplet. For example, MC Ren raps on "Straight Outta Compton":
"But I don’t give a fuck I’mma make my snaps
If not from the records, from jacking or craps
Just like burglary, the definition is jacking
And when illegally armed it’s called packing."
There is nothing overtly difficult or unique here about rhyming 'jacking' with 'packing,' but Ren still relays his lifestyle with accuracy.
Rap’s progression was imminent, just as it is in any other field. New inventions are made, evolution happens, and what was once tradition or standard soon becomes, to borrow a term directly from hip-hop, "old school." For the constant re-invention and evolution of the genre, we need inventive MCs to be at the helm, MCs who do not limit themselves to any sort of "standard." Kanye West is the master of invention, and reinvention. His sound has been remodeled (and progressed) from album to album, constantly keeping himself ahead of the curve. In terms of lyrics, Kanye isn’t known for overtly poetic bars, but that’s not necessarily what poetic license is about. Kanye isn’t afraid to stray from the set of rules that make up the English language in order to complete a rhyme scheme. When Yeezy wants to rhyme 'collagen' with 'apologizing' he just makes a new form of the word, re: "Can’t Tell Me Nothing."
"Don’t ever fix your lips like collagen
and say something when you gon’ end up apologing,"
This make the listener laugh, because it’s so obviously not a word, but, at the same time, Kanye clearly gets his point across-- it’s not like we’re left scratching our heads wondering what he’s trying to say, or why he didn’t say "apologizing." Our brain adjusts and comprehends, and we enjoy the bar that much more because it’s unusual. Great writers won’t let you dwell on a mispronunciation or a deviation from the rules. They get away with it.