John Mueller actually spoke about the issue in his Webmaster hangout on Friday afternoon at around 12:50pm EST, which was an hour and a half after Gary Illyes confirmed the update.
Here is Gary's confirmation tweet:
@rustybrick will. Obviously there was an update. Why would we deny that— Gary Illyes ᕕ( ᐛ )ᕗ (@methode) March 24, 2017
John Mueller at the 53:50 mark into the video was given a Fred quality and in his response, John cited "quality" six times and he didn't spend all that much time answering the question.
Here was the question:
Since the Fred update, oh my gosh, we’ve seen a gradual decline in our search rankings. We’ve followed all of the Google guidelines so we can’t understand why we’ve fallen so far. We were on top of page two, bottom of page one, (and now the lights are turning off again, because of Fred, Fred is turning off the lights). Any help that you can give us would be great.
Here is the answer:
Essentially, if you are following the Google guideliens and you are doing things technically right, then that sounds to me like there might just be just quality issues with regards to your site. Things that you can improve overall when it comes to the quality of the site.
Which means there is no simple kind of answer, like there is no meta tag that would make your web site higher quality. It is just in general, you probably need to take a step back, get random people who are interested in that topic to review your site compared to other sites to kind of go through a survey to see what you can be doing better to improve the quality of your site overall. And ideally, don’t just like tweak things to kind of subtly improve the quality to see if you can get a little higher. Really take a stab at it and try to figure out what you can do to make a significant dent in the quality of the site overall.
Here is the video embed where the Fred Q&A starts:
Forum discussion at Twitter.