Take the axioms of ZFC, Peano arithmetic, or some other familiar theory and try writing them down in a logic formalism that features only the NAND connective, and you’ll see what I’m talking about. (Better yet, try devising a formal proof system using such formalism!)
I don’t understand why this should be significantly easier, but I’ll take your word for it; a formal system is a formal system, I suppose.
Take the axioms of ZFC, Peano arithmetic, or some other familiar theory and try writing them down in a logic formalism that features only the NAND connective, and you’ll see what I’m talking about. (Better yet, try devising a formal proof system using such formalism!)