Success should be measured in different ways in different contexts. In the case of Mike D’Antoni or any other basketball coach, success is measured by wins and losses and, to some degree, in how far up the professional ladder one climbs. This tells us whether D'Antoni is successful professionally.
Of course, there are other aspects to success. A person’s professional life is only one aspect of their entire life. It is just as important to be a success as a person as it is to be a professional success. However, without knowing D’Antoni personally, there is no way we can say whether he is a personal success.
Professionally, we would have to say that D’Antoni is a success, though not a complete one. Anyone who becomes a coach in the NBA, the best basketball league in the world, has reached the pinnacle of the profession. D’Antoni has not only reached the NBA but has managed to coach parts of 11 seasons in the league. He is clearly a success in this sense. However, if we define “success” rigidly enough, D’Antoni has not been a complete success. He has not made it to the NBA Finals, and therefore has not won a championship. He is not the most respected coach in the game, with many saying that he can’t coach defense and that he can’t adjust his offense to fit the players he has.
Professionally, then, D’Antoni has clearly been a success. He is a long-term NBA coach with a winning record. He has not won a title and is not seen as one of the elite coaches in the league, but he has been successful.