Let me add that Heb 8:7 found the COVENANT to be faulty, not the Law. The covenant proved faulty because the Israelites breached it, and because it was taught by humans. The NEW covenant would be different. God himself would write it on their hearts, instead of man attempting to instill it in others.
Hebrews 8 continues to cite Jeremiah 31, and it's one the things that I'm continually baffled at regarding the huge amounts of printed literature from WT. The new covenant, in part, says: "‘And they will no longer teach each one his fellow citizen and each one his brother, saying: “Know Jehovah!” For they will all know me, from the least to the greatest of them." And yet, here we are studying a book called, "Draw Close to Jehovah". How's that for irony?