Saying that interacting on Substack bears fruit is not the same as saying that it does on all social media platforms. We've discussed that before. Algorithmic crunch forces paid advertising to get much of anywhere, and it's hard to get a positive ROI from it. One of the reasons Substack still has value is precisely because there is no paid advertising for an algorithm to favor. That's not to say that social media has no value, but at least, its value isn't as much as you claim.
Also, at the risk of being repetitive, when I looked at some of your social media not so long ago, you weren't practicing what you preach. I'm sure that's because of the demands of your day job and not because you don't believe what you're saying. But the point is, you speak authoritatively on something without even having full personal experience with it. Yes, you have studied branding and advertising a lot, clearly. But as I learned in education, practical experience often trumps theory, even when the theory is well founded. That's partly because human behavior is not as predictable as things governed by natural law, like gravity. And there are a huge number of variables.
Is branding important? Yes. Is spending time on every single social medium important? Not necessarily. Companies with large budgets still make it work. Companies that can afford a person to run social media (or even more than one) can still focus on doing things like developing new products without having to sacrifice manpower to social media.
I'd argue that authors experiment, find what works best for them, and then focus their energy there, rather than scattering it across every conceivable medium. That's what I've done. When I started, I got on several platforms and worked them all. in that era, that was actually more worth it. I started dropped them when returns no longer justified time (and money) spent. Facebook is a good example. It used to generate real fans. Now, the same process is much more time consuming, more expensive, and not worth it, at least for me. (Aside from money, I used to spend one and a half to two hours a day curating social media content. It's not as if I haven't given SM an ample chance.)
Here's an interesting case study, however, that shows FB can still be worth it. You all remember Amanda M. Lee, I'm sure. She used to post here. When last she mentioned income, she was making low seven figures a year, so I think we can agree that she's successful. The fact that she's a publishing machine with a new release practically every month may be the foundation of that success. What talent and self-discipline that must take! But she still feels it worthwhile to use FB.
https://www.facebook.com/AuthorAmandaMLee/She's active, but the frequency is lower than what you advocate, PJ (once a month most of the time, more in October) and entirely geared to things like new releases. This seems to be a books-are-the-brand approach. There doesn't seem to be much about her. Her blog, aside from a brief bio, is the same way. Books, books, books, books, books.
That said, about half of her FB posts are short book videos. I imagine she's using a content creator for those, so there would be money involved (or time, if not). These are way more impressive than what I see on the average author page, even from trad authors. If I had the money, I'd be tempted to try a similar approach. But of course, it also helps that she has one or more new releases a month. It's easy to have fresh content if you have fresh books at that frequency. It's not clear that one could achieve a similar level of FB engagement with a less frequent publishing model. We also don't know how much she used FB ads. She could easily be someone who got a fan base when FB is more productive and managed to hold on to it.
