Nine successful interceptions out of 17 doesn´t seem a very promising statistic to me, especially given that these results are often exaggerated.
Well still much better than zero. This is equivalent to the invention of practicle body armor against modern firearms back in the 20th century. It won't save you every time, but you'd feel safer having it. If the 17 largest cities in the US for example are targeted and destroyed by nukes, that seems like the end of America, but if 9 can survive, there might be a future for the country.