SEO has NEVER been certain, it has also never been static.
Google has made changes in the algo for years, they will continue to make changes.
As Google changes SEO changes right along with it.
5 years ago we used meta tags that we stuffed with keywords, now those tags have been devalued so much that they are no longer used.
4 years ago we used to make changes in our sites then sit on your hands and wait, now we make a title tag change and it is indexed by afternoon tea.
3 years ago we used to tweak our content, tags, titles, then we had to wait for the "Google Dance" that only happened once a quarter or so....THAT would shift all the SERPS up down and sideways...now, SERPS happen overnight...
Now we have image search, php sites are searchable, videos....
In the grand scheme of things SEO has always shifted, and thus what the ALGO values or devalues is also shifting. So yes links values have also shifted as they always have.
Understanding SEO is understanding an entire concept, not just bits and pieces....
The broad concept is that Google is fighting is SEO for SEO's sake & not for peoples sake. The people & SEO companies who understand that will always be ahead of the pack, those that don't will be left behind in the SERPS.