I am not a Monetarist and I believe he said, later in life, that targeting money supply wasn't as worthwhile a practice as it had been previously. Nonetheless, he remains my favorite economist and one of my favorite defenders of liberty.
Part of the reason the Monetarist have lost their following is due to a number of factors, including losing their best spokesman. More complicated though are the “near monies” that are not controlled by factors the Monetarists advocate and control. I also think the relative price stability that’s followed the Carter years with his 21% prime interest rate has resulted in a de-emphasis on Monetary policy.