Have online publications quit using Flickr as a source of free photos? I don't know.
Are Flickr stats no longer effectively reporting off-site links? Who knows; Flickr is constantly messing with things under the hood and out of sight.
Are there fewer online publications? Possibly; I've noticed that small-scale blogs, which often used my images, seem to be falling dormant or ceasing publication altogether.
A more likely explanation, however, is that I have been posting fewer images to Flickr this past year or two, the images I post are low-grade snapshots and not very interesting, and I moved many of my most popular images (Thailand and Spain travel photos, in particular) to iPernity. And nobody looks at iPernity!
I'm going to try to post more and better photos in 2016, and see if that makes a difference. I might even resurrect a "365" project or two!