NY rap is full of guys who had great debut albums, or even multiple albums, but never reached that next level. Nas could have easily released an album full of Deja Vu type tracks or let Marly Marl handle things, and I'm sure hip hop purists would love that (as would we). But the fact is that he likely would not have taken that next step, and instead would be another KRS, OC, GZA, G Rap, etc career wise. Illmatic is a classic and arguably the greatest rap album ever, but I agree with others who have said IWW is the album that secured Nas' career and put him on the path to prolonged greatness.
And it's not like he put out a pop rap album or some shyt, or had multiple "rap n bullshyt" tracks. That shyt is more street than Life After Death, real talk.