What's changed about SEO?

I learned about SEO around 2012. Since then, I know that it has changed; social/sharing is more important, keywords less so.

One correction I'd make: social/sharing isn't that important; keywords (and keyword phrases on a page) are the primary way Google knows what a page is about.

The most important factor? High-quality and relevant links from sites in the same general industry. Those are what get you ranking — and most often if you see a competitor outranking you and they aren't doing social or writing articles or any other best practices, it's because they're focused on building relationships that result in high-quality links to their site.