As rap progressed across the decades, the 'message' in the original form was a new style of beat poetry based on the jive and the street talk in the Afro/American communities of the day. The lyrical content was local, it referenced the culture people saw all around them, the life and the social conditions they lived in and how they communicated their opinions and grievances.
But as it progressed through the millennium period to today, it became far more violent and misogynistic, it referenced money and wealth, grabbing the cash and flashing it around. Having bitches and whores, fast cars, jewelry, power, tossing cash, gold teeth, and the classic full tracksuit as the new style on the streets. The sportswear as a suit type statement, with the massive gold chains and huge rings on the fingers were the ostentatious signs of success - in terms of wealth. Along with a new pair of Nike/Puma/Adidas sneakers every other day was now the parallel of the white man's business suit and handmade shoes. It had a sort of rebellious punk ethic to it. A new way of showing your wealth and at the same time giving two fingers to convention.
Chuck D made point that, for all the money the Afro/American population spent on designer sports gear from all the big names, that these companies never put anything back into the communities that made them so wealthy right across the globe. So the political messages from the late 80's through to today had some degree of parallel, but the scope was getting wider all the time. By now there's no rule book at all. You can rap about whatever the fuck you like and nobody is shocked by any of it. There aren't any subjects that are untouchable - everything is up for judgement. But the lowest common denominator still applies: if you want to get rich in the music business these days, you'd better have something new, a new barrier to break down.
Politically speaking, nobody has yet surpassed the work of Gil Scott Heron, Afro/American, author, poet, and songwriter. He didn't dilute his statements to suit television or radio. That wasn't his base anyway, but still - modern America had a hard time from Heron, he didn't mince his words. He went for the jugular every time, and it took a long, long time for Heron's work to be appreciated for what he did. Like here, his angle on the Reagan era with references to the McCarthy trials and fear of the big bad communist wolf. The sad thing is that nobody has come close to doing what he did both politically and musically. Many have tried, but none have succeeded.