It is as you describe, but I think the increasing proportion of mediocre (to say the least) content is quite normal and inevitable in fact. The challenge is to find the pearls that are hidden in the bulk of posts and I would wish we would have some more options to filter the different feeds. In the absence of intelligent filters I recommend to take the time building yourself a quality home feed. A good starting point to speed up populating your home feed is to check for the resteemed posts in those blogs that you are already following for good reason.
And most importantly, upvote the content that you like to see more of.

Cheers,
Shaka