Every rapper has a knock or two that under a microscope is bullshyt.
Nas NEVER had a bad ear for beats. You don't sell over 30 Million records worldwide with bad beat picking.
Nas, by his own admission, went left sonically after Stillmatic. He doubled down on Boom Bap when the popular sound was The Neptunes, Scott Storch, and the South coming up with Lil Jon. Funny thing is Nas worked with all of them during the time, just not on his own albums. He drew for Alchemist before Alch was a household name. He put Ron Browz on the map (Ether) He did some INCREDIBLE work with Salaam Remi (Who was basically his Just Blaze) and this was only a two album cycle (Gods Son/Streets Disciple) by the time Nas signed with Def Jam he was back working with the quote unquote top producers of the era (Kanye West, Dr Dre, Will I Am, and Stargate all did production on Hip Hop Is Dead) Salaam only has one beat apiece on HHID and Untitled, and by the time Life Is Good came around, Salaam was seen as a prestige producer who crafted classics for legends like Nas, Sade, and Amy Whinehouse. His beats were NEVER wack, maybe unorthodox, but only from the standpoint of attempting to update the classic New York Boom Bap sound, which again, by the time Life Is Good dropped, everyone was embracing.