Can Someone Explain G SERP Changes to Me?

I haven't been keeping up, I'm sorry, and I'm sure there have been major changes and discussions here regarding the algo since I was watching like a hawk.

Anyway, I've noticed this change recently as a Google user.

It used to be that the following search:

keyword "keyword phrase"

Would return only pages that contained both "keyword" and "keyword phrase."

Example search:
shotgun "water density"

The only pages returned would include the term "shotgun" and the phrase "water density."

Now, you get a bunch of pages that contain "water density," but no "shotgun;" and a bunch of pages that contain "shotgun," but not "water density."

This changed in the past year, and I feel that SERPs have been diluted with crap quite a bit.

I used to regularly use Google to search for very specific things, and include for instance, a common academic term (e.g. "paradoxically," "paradigm," "theorem") and get very good results.

Now, it seems like the algo just omits the least common phrase or term from the search.

What happened?

Any useful links?

TIA

 

Google is the not the same one as it was one year ago....

Only Google can answer this...