I agree with @Flumen. There are all kinds of factors that affect sales and visibility of new tracks. It is probably safe to say that Elements and the “Experiments” are playing some part in making it more challenging to sell music, themes, videos, etc.
But above all else, the growth of available options (at this marketplace, and in the industry, in general) is the #1 issue that is making it more difficult to sell your digital assets.
There’s a lot of good stuff out there, and the bar has been raised. Your stuff has to be really good, really useful, and above all, I think, really unique, in order to have a chance to stand out.