Most SEO consultants would concurr that the links pointing at your website remain a major ranking factor on Google (that's why there are so many businesses offering to sell backlinks).
From what I see, my approach is different to many in the SEO world when it comes to link building. I offer manual link building services based on competitor analysis to bring traffic and boost rankings (I don't buy backlinks which is against Google's guidelines) and outine content strategies to earn links to your website.
Even though Google may find it hard to detect all unnatatural paid links, your competitors can easily detect some of them using common (free) backlink checker tools and report them to Google.