The simple and sad truth is that Macklemore can make any song he wants because he is given the freedom to do so. A lot of it happens to do with the fact he is white. Not race baiting or trying to talk down on him for being a white rapper but there is a lot of truth to it. He gets the benefit of the doubt and he's not threatening.
Outside of J Cole or Kendrick, the label pushes your product when you do what the label wants. That is why certain rappers put out the same songs. If they don't listen and fall into line, people stop taking their calls and their records stop getting pushed. As soon as Nelly stopped wanting to make those corny same old dance songs, what happened? When he tried to do more heart felt songs? If you don't run the play the coach wants, you get benched. Plain and simple.
And before anyone says 'oh those rappers like Nelly just lost their talent' the guy had other people writing for him at his peak. .A lot of them do. So it's not about Nelly not being able to make a catchy hook anymore, it's more like his label stopped wanting to put the resources together if he wasn't going to play his position.