My Millennial daughter gets paid big bucks for handling the social media of several client businesses (and, dang, it is really a shark-infested pool!). I'm also in touch with several good friends who are Millennial photographers making heavy use of social media for marketing.
For commercial photographers, it's getting to the point that photographers are not getting jobs by the quality of their work, but by their own social media influence. Their clients are banking on the reach the photographers have already accrued (and that might not be by good photography) to help sell their products.
My young friends have become slaves to doing whatever it takes (and shooting whatever it takes) to gain likes and following, and it's a day-by-day, minute-by-minute struggle for them. Every time they post something, they have to study the effect that picture has on their following, then adjust whatever they do to meet the trend. They admit to me that it sucks.
As a retail consumer photographer (portraits and such), I'm coming away with this understanding. As as a direct-to-consumer photographer, I don't need to be a social media influence myself. What I really want are clients who are social media influences. The social media influence of my clients equals what used to be "word of mouth."
It appears that gaining such clients hasn't changed too much from the past methods. I'm getting good results reaching such clients with displays where they "congregate." I get my best results from a display in a high-end hair salon, where prospects have nothing to do for long periods of time but sit and look at my large wall prints. I do a "free" family portrait session for the owner each year, and she steers customers to me, particularly after they've had expensive styles done.
Those women tend to have their own heavy social media influence, so when they post my images and tag me, it's their following that counts.