For me to buy that argument, Nas can't be the only GOAT level rapper with great rapping ability who gets dismissed like that. If people were downplaying Jay similarly I'd say ok you have a point, but that doesn't happen. For some reason Nas gets dismissed and criticized in ways few others do. And I think it's because he hasn't had a hit in decades. Because of that, a lot (not most) people view him closer to Big/Pac in the GOAT discussion in terms of being "the past," ie stagnant. Verses more active GOAT candidates who have hit songs and albums over the last few years like Jay or Wayne.
I'm in my early 30s. The "Mount Rushmore" of rap for me, and many Coli people, is Nas/Pac/Jay/Biggie. But the Mount Rushmore of rap for the generation after us differs drastically. Wayne is there for sure. Jay is there for sure. Kanye is probably there. And then it kinda depends on what you like or where you're from. Gucci, Drake, Kendrick, Cole, Future, etc. Basically we're watching Biggie and Pac move into the past - not forgotten, but no longer prioritized. It's a conversation/situation LL Cool J/Rakim/BDK/KRS fans went through in the mid 90s, when they saw the new generation completely move on from their heroes. Unfortunately I think a lot of people view Nas in that "past" category, and it's why some people don't even count him. They don't wanna hear it.