Welcome to WebmasterWorld Guest from 188.8.131.52
IMO, and I'd love to be proven wrong, Penguin was a lot more than an attack on bad link profiles. In my travel niche, every "freeloader" site that made money off free traffic from Google SERP's disappeared post Penguin and have never recovered. The replacements were all the authority affiliate sites we see today.
Google has never made a secret of its dislike for thin affiliate sites.
useful pages with affiliate links can rank quite well in Google, and those affiliate links can produce significant income
But if there are multiple pages that promote and link to affiliate products, then there is a clear signal the site is intentionally soliciting affiliate transactions. I wonder if that is a tipping point for Google to determine what is an affiliate site and what is not?
A number of years ago, one of our pages of affiliate links was featured in a leaked Google quality raters' manual as an example of a "good" affiliate page. The accompanying text said that we added value with articles and other content. Interestingly enough, the page itself was simply an organized list of affiliate links. Most of the cited "added value" wasn't on that page, but was elsewhere on the site.