At it's core SEO boils down to a protocol for helping search engines make sense of your website/content. If you look at it that way, then yes SEO still works in 2018.
But more often than not, SEO is an umbrella term which encapsulates both the good and the bad practices. Given the work Google and others have done on weeding out the latter using ML/AI as well as human intervention [0] I would say you can't be sure whether those would work. It's contingent on Search Engines being aware of the practice and penalizing that behavior. So it may work today but not guaranteed to work tomorrow.