According to Google, thin affiliates or participating in affiliate programs without adding sufficient value is consider a low-quality signal. “Flight by night”, cookie-cutter, mad lib websites – or however you want to call them – were never on the “like” side at Google:
“Google believes that pure, or “thin,” affiliate websites do not provide additional value for web users […] Pure affiliate sites consisting of content that appears in many other places on the web are highly unlikely to perform well in Google search results and may be negatively perceived by search engines” source
“Here are a few common examples of pages that often have thin content with little or no added value: […] Thin affiliate pages. source
[…] These techniques don’t provide users with substantially unique or valuable content, and are in violation of our Webmaster Guidelines. As a result, Google has applied a manual spam action to the affected portions of your site.” source
That being said, not all affiliate sites are bad. If you add value, Google is not going to demote your affiliate website, just because you’re selling something.