The simple fact of the matter is that, as an Internet marketer, you need something better than artificial link building and pages of useless, jumbled nonsense to get long-lasting traffic referrals from major search engines such as Google, Bing and Yahoo. Google in particular pays special attention to your visitors' behavior. So if visitors are quickly navigating elsewhere because your site is full of junk content, then you will get fewer traffic referrals from Google over the long run.
Imo it is not possible for google to detect properly spun content, it is not worth computing power it requires. They can do this using ngrams for example, but it is uses a lot of queries. And for example article spinner I coded beats this algo, so google cant detect that the content is spun. Manual spinning is also good but it takes more than 30 minutes per article.