I'm not sure if they’ve added any monetization features over the years. Back then, it was arguably the best platform for getting discovered as a producer or DJ. When I stopped making music, I was getting a lot of requests to play at clubs across Germany and Europe.
At the time, I preferred to stay anonymous, so I never made the leap into the professional or public scene. Still, I was in touch with some producers early in their careers on SoundCloud when they had 1000 followers, like Robin Schulz and Felix Jaehn, if those names ring a bell.
So yes, I’d say it was (is?) definitely a launchpad for artists. But as far as I know, there was never a real way to monetize on the platform.
Unfortunately, when I stopped paying for the Pro version, they removed almost all of my music. Only 5 mixes are still up :')