Aldo reigned in an era where FW didn’t even exist yet in the UFC. The division was still thin.
He also fought a lot of wrestlers and Aldo was tailor made to beat wrestlers probably best takedown defense in the game.
Aldo didn’t face too many great strikers during his reign ( best one being Mark Hominick ). He ran into issues as soon as he faced great strikers in McGregor, Holloway, and Volk.
Aldo isn’t goat because he reigned in a era that was simply too early and he couldn’t make it in the next one.