I agree with the share for traffic not for links statement.
Many social media posts do end up counting as links. Even if the links don't count it is brand mentions, URL mentions, and coverage.
Social media can be very powerful. There is a lot to making an effective social media campaign. Posting at the right times on the right platform to the right audience is critical. The half life of a tweet vs a linked in article is drastically different.
Organic reach on social media platforms is dwindling but there are still a lot of opportunities.
It also augments SEO very well, as SEO is the long game and Social media and PPC is immediate. All are effective. SEO provides the best ROI in the long term, just business operates on short, medium and long term horizons. When you need results now Social media and PPC are great options.