I am not sure what you meant by old school seo tactics, whether you are referencing to black hat link building to jump serps. But as far as SEO as a whole is concerned if you follow Google guidelines and do ethical link building like guest blogging, Blog commenting, link baiting, directories etc. These tactics are still working great.
As far as social sharing is concerned. Social signals is one of the metrics which Google takes into account when ranking a website. SO more shares, likes, tweets means better ranking. But social is just one factor.
No. Social media is just one tiny way you can help with SEO. Link Building and landing pages are still the majority method of attracting relevant visitors from organic search.