Penguin came about a couple years ago, because the search results were bad due to the effectiveness of linkspam. You could rank anything for everything with a good domain name, one page of text and thousands of automated spam links. Penguin penalized sites which had a lot of those types of links and used exclusively keywords as anchor text. That eventually led to people discovering that they could spam their competitor and have them get a penalty next time around. This Penguin was supposed to be better at discerning so called negative SEO.
New Google updates work on aggregate probability data. They use human raters to rate thousands of websites from authority to spam/scam, then use algorithmic machine learning to figure out what spammy sites have in common and what authority sites have in common. That's why trying to trick Google becomes ever harder. There are patterns in link profiles and Penguin targets certain patterns.
Linkbuilding is still very effective, but needs to be done with caution. Either go full spam and enjoy the spoils until next update or focus on links which bring traffic.
New Google updates work on aggregate probability data. They use human raters to rate thousands of websites from authority to spam/scam, then use algorithmic machine learning to figure out what spammy sites have in common and what authority sites have in common. That's why trying to trick Google becomes ever harder. There are patterns in link profiles and Penguin targets certain patterns.
Linkbuilding is still very effective, but needs to be done with caution. Either go full spam and enjoy the spoils until next update or focus on links which bring traffic.