I dont think they are devaluing blogs, I do think they are "trying" rank them better. My blog doesnt show up much in general serps and its been showing up less and less as the year goes on. But under the blog tabs its quite visable.
If I have a post/page about "Red widgets" my blog tends not to show up for the search term "widget" in the serps( regardless of how i optmize it). However in "blogs" it shows up fine
I feel like they are compartmentalizing far more then they used to