Horst is the architect of the failures through his trades, and deals with free agents. He's let guys like Tucker slip away, when they had them, and would have let Crowder go at the end of this past year, if it hadn't been for a coaching change.
He doesn't find players that actually add to the team, he finds players that offer alternatives, but in the end, no matter how many points Lillard scores it isn't going to make up for the fact that the Bucks no longer have a point guard who plays solid D, and it's essential in the way this team operates on the floor.
If they fail this year, and it appears they will, and miserably, Horst will find himself on the outside looking in. In my mind, the sooner the better. He is a failure when it comes to judging talent.