Are DJs musicians?
In my opinion, undoubtedly yes.
While they aren't creating the raw sound, they are putting it together and layering it in innovative ways. Their creative input lies at a higher level of abstraction than people who have to create the raw sound (singers, instrumentalists). Their performative showmanship lies in sensing the energy of the crowd and guiding it through highs and lows.
We are about to witness "the great dj-fication" - a world where anything and everything is remixable. A world where the cost of creating building blocks for literally anything is going to go tend to zero. What's going to change when this happens? Who will thrive in this world?
In my opinion, the biggest winners (and there are several) are people with big ideas and good taste. These are the people who'll be able to tell the difference between generated content that is good, and generated content that is garbage. These are the people who have an understanding of "which kind" of content serves the bigger picture.
Like DJs, they don't need to be experts in creating the raw content itself (though that will certainly help!), but more importantly they need to have a very coherent high level idea of how the pieces fit together to form something great. This might even involve a lot of trial and error, but if testing samples is fast and cheap - then being able to "know it when you see it" becomes really valuable.
The next decade is going to be pretty wild! :)