Big L was brilliant. "Lifestylez Of Da Poor & Dangerous" and "Big Picture" are awesome albums.
It's really a case of "What might have been".
As for not being able to write songs, untrue at all. He was an adept commercial artist "Put It On", "MVP", "Holdin It Down", with good storytelling ability - "Casualties of A Dice Game", "Devil's Son", and he was good as making positive songs too, and coming up with original concepts, like "Ebonics".
I firmly believe he would have had a hit record, had he lived.