Some good thoughts here! I don't think the price is plummeting as a direct result of too many steemit or steem related posts, but I do think that having non steemit related posts on trending is likely to attract a wider range of audience and potentially a larger audience overall.
I know for me personally, if I showed up to a blogging platform and saw a diverse group of topics making $50+ dollars I would sign up immediately. If I showed up to a blogging platform where only Steemit and Steem related posts were making $50+ I am not sure I would be as quick to join...
Yes, the drop can not be completely blamed on that, but I think a significant reason why it is not increasing has been due to the fact that new users feel slightly intimidated by these articles. Your personal feeling is pretty much the same as mine, thanks for the feedback!