On site SEO can still make a massive difference. I was recently building out a Stocking Fillers website, and in my research I noticed that a site went from number ten in the serps one day, to number one the next.
The difference seemed to be that they previously had the https version indexed.
The reason for their increase in ranking could be:
- They are no longer splitting the page rank / link equity to two versions of the URL.
- The https is slower to load and if Google are indexing that, it can impact the rankings.