I'm surprised that people don't know where this narrative comes from.
Nas seems to be one of them rappers that would write rhymes without hearing beats first.
So while the rhymes were ill they could sound out of place over certain beats. And since you couldn't criticize the rhymes you were left with criticizing the beat to explain why something sounded off
I assumed it came from groing from production on Illmatic,to it being downhill ever since. So its more like he has the cache to get better beats,but seems to cheap out on the production side. Albums like I Am and Nastradamus have aged even more horribly,not that they were good in the first place. But the beats didnt stand out as bad to me in real time. The songs just arent that good.
His beats didnt bother me that much,because thats not really his thing. Your going to be focused on catching his lyrics,and hes not making music for the whip.
Most of the goats had great production at various points or during a stretch though. So it has to come up during the rankings.